1// Algorithm implementation -*- C++ -*-
2
3// Copyright (C) 2001-2013 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library.  This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
23// <http://www.gnu.org/licenses/>.
24
25/*
26 *
27 * Copyright (c) 1994
28 * Hewlett-Packard Company
29 *
30 * Permission to use, copy, modify, distribute and sell this software
31 * and its documentation for any purpose is hereby granted without fee,
32 * provided that the above copyright notice appear in all copies and
33 * that both that copyright notice and this permission notice appear
34 * in supporting documentation.  Hewlett-Packard Company makes no
35 * representations about the suitability of this software for any
36 * purpose.  It is provided "as is" without express or implied warranty.
37 *
38 *
39 * Copyright (c) 1996
40 * Silicon Graphics Computer Systems, Inc.
41 *
42 * Permission to use, copy, modify, distribute and sell this software
43 * and its documentation for any purpose is hereby granted without fee,
44 * provided that the above copyright notice appear in all copies and
45 * that both that copyright notice and this permission notice appear
46 * in supporting documentation.  Silicon Graphics makes no
47 * representations about the suitability of this software for any
48 * purpose.  It is provided "as is" without express or implied warranty.
49 */
50
51/** @file bits/stl_algo.h
52 *  This is an internal header file, included by other library headers.
53 *  Do not attempt to use it directly. @headername{algorithm}
54 */
55
56#ifndef _STL_ALGO_H
57#define _STL_ALGO_H 1
58
59#include <cstdlib>             // for rand
60#include <bits/algorithmfwd.h>
61#include <bits/stl_heap.h>
62#include <bits/stl_tempbuf.h>  // for _Temporary_buffer
63
64#if __cplusplus >= 201103L
65#include <random>     // for std::uniform_int_distribution
66#include <functional> // for std::bind
67#endif
68
69// See concept_check.h for the __glibcxx_*_requires macros.
70
71namespace std _GLIBCXX_VISIBILITY(default)
72{
73_GLIBCXX_BEGIN_NAMESPACE_VERSION
74
75  /// Swaps the median value of *__a, *__b and *__c to *__result
76  template<typename _Iterator>
77    void
78    __move_median_to_first(_Iterator __result, _Iterator __a,
79			   _Iterator __b, _Iterator __c)
80    {
81      // concept requirements
82      __glibcxx_function_requires(_LessThanComparableConcept<
83	    typename iterator_traits<_Iterator>::value_type>)
84
85      if (*__a < *__b)
86	{
87	  if (*__b < *__c)
88	    std::iter_swap(__result, __b);
89	  else if (*__a < *__c)
90	    std::iter_swap(__result, __c);
91	  else
92	    std::iter_swap(__result, __a);
93	}
94      else if (*__a < *__c)
95      	std::iter_swap(__result, __a);
96      else if (*__b < *__c)
97	std::iter_swap(__result, __c);
98      else
99	std::iter_swap(__result, __b);
100    }
101
102  /// Swaps the median value of *__a, *__b and *__c under __comp to *__result
103  template<typename _Iterator, typename _Compare>
104    void
105    __move_median_to_first(_Iterator __result, _Iterator __a,
106			   _Iterator __b, _Iterator __c,
107			   _Compare __comp)
108    {
109      // concept requirements
110      __glibcxx_function_requires(_BinaryFunctionConcept<_Compare, bool,
111	    typename iterator_traits<_Iterator>::value_type,
112	    typename iterator_traits<_Iterator>::value_type>)
113
114      if (__comp(*__a, *__b))
115	{
116	  if (__comp(*__b, *__c))
117	    std::iter_swap(__result, __b);
118	  else if (__comp(*__a, *__c))
119	    std::iter_swap(__result, __c);
120	  else
121	    std::iter_swap(__result, __a);
122	}
123      else if (__comp(*__a, *__c))
124	std::iter_swap(__result, __a);
125      else if (__comp(*__b, *__c))
126	std::iter_swap(__result, __c);
127      else
128	std::iter_swap(__result, __b);
129    }
130
131  // for_each
132
133  /// This is an overload used by find() for the Input Iterator case.
134  template<typename _InputIterator, typename _Tp>
135    inline _InputIterator
136    __find(_InputIterator __first, _InputIterator __last,
137	   const _Tp& __val, input_iterator_tag)
138    {
139      while (__first != __last && !(*__first == __val))
140	++__first;
141      return __first;
142    }
143
144  /// This is an overload used by find_if() for the Input Iterator case.
145  template<typename _InputIterator, typename _Predicate>
146    inline _InputIterator
147    __find_if(_InputIterator __first, _InputIterator __last,
148	      _Predicate __pred, input_iterator_tag)
149    {
150      while (__first != __last && !bool(__pred(*__first)))
151	++__first;
152      return __first;
153    }
154
155  /// This is an overload used by find() for the RAI case.
156  template<typename _RandomAccessIterator, typename _Tp>
157    _RandomAccessIterator
158    __find(_RandomAccessIterator __first, _RandomAccessIterator __last,
159	   const _Tp& __val, random_access_iterator_tag)
160    {
161      typename iterator_traits<_RandomAccessIterator>::difference_type
162	__trip_count = (__last - __first) >> 2;
163
164      for (; __trip_count > 0; --__trip_count)
165	{
166	  if (*__first == __val)
167	    return __first;
168	  ++__first;
169
170	  if (*__first == __val)
171	    return __first;
172	  ++__first;
173
174	  if (*__first == __val)
175	    return __first;
176	  ++__first;
177
178	  if (*__first == __val)
179	    return __first;
180	  ++__first;
181	}
182
183      switch (__last - __first)
184	{
185	case 3:
186	  if (*__first == __val)
187	    return __first;
188	  ++__first;
189	case 2:
190	  if (*__first == __val)
191	    return __first;
192	  ++__first;
193	case 1:
194	  if (*__first == __val)
195	    return __first;
196	  ++__first;
197	case 0:
198	default:
199	  return __last;
200	}
201    }
202
203  /// This is an overload used by find_if() for the RAI case.
204  template<typename _RandomAccessIterator, typename _Predicate>
205    _RandomAccessIterator
206    __find_if(_RandomAccessIterator __first, _RandomAccessIterator __last,
207	      _Predicate __pred, random_access_iterator_tag)
208    {
209      typename iterator_traits<_RandomAccessIterator>::difference_type
210	__trip_count = (__last - __first) >> 2;
211
212      for (; __trip_count > 0; --__trip_count)
213	{
214	  if (__pred(*__first))
215	    return __first;
216	  ++__first;
217
218	  if (__pred(*__first))
219	    return __first;
220	  ++__first;
221
222	  if (__pred(*__first))
223	    return __first;
224	  ++__first;
225
226	  if (__pred(*__first))
227	    return __first;
228	  ++__first;
229	}
230
231      switch (__last - __first)
232	{
233	case 3:
234	  if (__pred(*__first))
235	    return __first;
236	  ++__first;
237	case 2:
238	  if (__pred(*__first))
239	    return __first;
240	  ++__first;
241	case 1:
242	  if (__pred(*__first))
243	    return __first;
244	  ++__first;
245	case 0:
246	default:
247	  return __last;
248	}
249    }
250
251  /// This is an overload used by find_if_not() for the Input Iterator case.
252  template<typename _InputIterator, typename _Predicate>
253    inline _InputIterator
254    __find_if_not(_InputIterator __first, _InputIterator __last,
255		  _Predicate __pred, input_iterator_tag)
256    {
257      while (__first != __last && bool(__pred(*__first)))
258	++__first;
259      return __first;
260    }
261
262  /// This is an overload used by find_if_not() for the RAI case.
263  template<typename _RandomAccessIterator, typename _Predicate>
264    _RandomAccessIterator
265    __find_if_not(_RandomAccessIterator __first, _RandomAccessIterator __last,
266		  _Predicate __pred, random_access_iterator_tag)
267    {
268      typename iterator_traits<_RandomAccessIterator>::difference_type
269	__trip_count = (__last - __first) >> 2;
270
271      for (; __trip_count > 0; --__trip_count)
272	{
273	  if (!bool(__pred(*__first)))
274	    return __first;
275	  ++__first;
276
277	  if (!bool(__pred(*__first)))
278	    return __first;
279	  ++__first;
280
281	  if (!bool(__pred(*__first)))
282	    return __first;
283	  ++__first;
284
285	  if (!bool(__pred(*__first)))
286	    return __first;
287	  ++__first;
288	}
289
290      switch (__last - __first)
291	{
292	case 3:
293	  if (!bool(__pred(*__first)))
294	    return __first;
295	  ++__first;
296	case 2:
297	  if (!bool(__pred(*__first)))
298	    return __first;
299	  ++__first;
300	case 1:
301	  if (!bool(__pred(*__first)))
302	    return __first;
303	  ++__first;
304	case 0:
305	default:
306	  return __last;
307	}
308    }
309
310  /// Provided for stable_partition to use.
311  template<typename _InputIterator, typename _Predicate>
312    inline _InputIterator
313    __find_if_not(_InputIterator __first, _InputIterator __last,
314		  _Predicate __pred)
315    {
316      return std::__find_if_not(__first, __last, __pred,
317				std::__iterator_category(__first));
318    }
319
320  /// Like find_if_not(), but uses and updates a count of the
321  /// remaining range length instead of comparing against an end
322  /// iterator.
323  template<typename _InputIterator, typename _Predicate, typename _Distance>
324    _InputIterator
325    __find_if_not_n(_InputIterator __first, _Distance& __len, _Predicate __pred)
326    {
327      for (; __len; --__len, ++__first)
328	if (!bool(__pred(*__first)))
329	  break;
330      return __first;
331    }
332
333  // set_difference
334  // set_intersection
335  // set_symmetric_difference
336  // set_union
337  // for_each
338  // find
339  // find_if
340  // find_first_of
341  // adjacent_find
342  // count
343  // count_if
344  // search
345
346  /**
347   *  This is an uglified
348   *  search_n(_ForwardIterator, _ForwardIterator, _Integer, const _Tp&)
349   *  overloaded for forward iterators.
350  */
351  template<typename _ForwardIterator, typename _Integer, typename _Tp>
352    _ForwardIterator
353    __search_n(_ForwardIterator __first, _ForwardIterator __last,
354	       _Integer __count, const _Tp& __val,
355	       std::forward_iterator_tag)
356    {
357      __first = _GLIBCXX_STD_A::find(__first, __last, __val);
358      while (__first != __last)
359	{
360	  typename iterator_traits<_ForwardIterator>::difference_type
361	    __n = __count;
362	  _ForwardIterator __i = __first;
363	  ++__i;
364	  while (__i != __last && __n != 1 && *__i == __val)
365	    {
366	      ++__i;
367	      --__n;
368	    }
369	  if (__n == 1)
370	    return __first;
371	  if (__i == __last)
372	    return __last;
373	  __first = _GLIBCXX_STD_A::find(++__i, __last, __val);
374	}
375      return __last;
376    }
377
378  /**
379   *  This is an uglified
380   *  search_n(_ForwardIterator, _ForwardIterator, _Integer, const _Tp&)
381   *  overloaded for random access iterators.
382  */
383  template<typename _RandomAccessIter, typename _Integer, typename _Tp>
384    _RandomAccessIter
385    __search_n(_RandomAccessIter __first, _RandomAccessIter __last,
386	       _Integer __count, const _Tp& __val,
387	       std::random_access_iterator_tag)
388    {
389
390      typedef typename std::iterator_traits<_RandomAccessIter>::difference_type
391	_DistanceType;
392
393      _DistanceType __tailSize = __last - __first;
394      _DistanceType __remainder = __count;
395
396      while (__remainder <= __tailSize) // the main loop...
397	{
398	  __first += __remainder;
399	  __tailSize -= __remainder;
400	  // __first here is always pointing to one past the last element of
401	  // next possible match.
402	  _RandomAccessIter __backTrack = __first;
403	  while (*--__backTrack == __val)
404	    {
405	      if (--__remainder == 0)
406	        return (__first - __count); // Success
407	    }
408	  __remainder = __count + 1 - (__first - __backTrack);
409	}
410      return __last; // Failure
411    }
412
413  // search_n
414
415  /**
416   *  This is an uglified
417   *  search_n(_ForwardIterator, _ForwardIterator, _Integer, const _Tp&,
418   *	       _BinaryPredicate)
419   *  overloaded for forward iterators.
420  */
421  template<typename _ForwardIterator, typename _Integer, typename _Tp,
422           typename _BinaryPredicate>
423    _ForwardIterator
424    __search_n(_ForwardIterator __first, _ForwardIterator __last,
425	       _Integer __count, const _Tp& __val,
426	       _BinaryPredicate __binary_pred, std::forward_iterator_tag)
427    {
428      while (__first != __last && !bool(__binary_pred(*__first, __val)))
429        ++__first;
430
431      while (__first != __last)
432	{
433	  typename iterator_traits<_ForwardIterator>::difference_type
434	    __n = __count;
435	  _ForwardIterator __i = __first;
436	  ++__i;
437	  while (__i != __last && __n != 1 && bool(__binary_pred(*__i, __val)))
438	    {
439	      ++__i;
440	      --__n;
441	    }
442	  if (__n == 1)
443	    return __first;
444	  if (__i == __last)
445	    return __last;
446	  __first = ++__i;
447	  while (__first != __last
448		 && !bool(__binary_pred(*__first, __val)))
449	    ++__first;
450	}
451      return __last;
452    }
453
454  /**
455   *  This is an uglified
456   *  search_n(_ForwardIterator, _ForwardIterator, _Integer, const _Tp&,
457   *	       _BinaryPredicate)
458   *  overloaded for random access iterators.
459  */
460  template<typename _RandomAccessIter, typename _Integer, typename _Tp,
461	   typename _BinaryPredicate>
462    _RandomAccessIter
463    __search_n(_RandomAccessIter __first, _RandomAccessIter __last,
464	       _Integer __count, const _Tp& __val,
465	       _BinaryPredicate __binary_pred, std::random_access_iterator_tag)
466    {
467
468      typedef typename std::iterator_traits<_RandomAccessIter>::difference_type
469	_DistanceType;
470
471      _DistanceType __tailSize = __last - __first;
472      _DistanceType __remainder = __count;
473
474      while (__remainder <= __tailSize) // the main loop...
475	{
476	  __first += __remainder;
477	  __tailSize -= __remainder;
478	  // __first here is always pointing to one past the last element of
479	  // next possible match.
480	  _RandomAccessIter __backTrack = __first;
481	  while (__binary_pred(*--__backTrack, __val))
482	    {
483	      if (--__remainder == 0)
484	        return (__first - __count); // Success
485	    }
486	  __remainder = __count + 1 - (__first - __backTrack);
487	}
488      return __last; // Failure
489    }
490
491  // find_end for forward iterators.
492  template<typename _ForwardIterator1, typename _ForwardIterator2>
493    _ForwardIterator1
494    __find_end(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
495	       _ForwardIterator2 __first2, _ForwardIterator2 __last2,
496	       forward_iterator_tag, forward_iterator_tag)
497    {
498      if (__first2 == __last2)
499	return __last1;
500      else
501	{
502	  _ForwardIterator1 __result = __last1;
503	  while (1)
504	    {
505	      _ForwardIterator1 __new_result
506		= _GLIBCXX_STD_A::search(__first1, __last1, __first2, __last2);
507	      if (__new_result == __last1)
508		return __result;
509	      else
510		{
511		  __result = __new_result;
512		  __first1 = __new_result;
513		  ++__first1;
514		}
515	    }
516	}
517    }
518
519  template<typename _ForwardIterator1, typename _ForwardIterator2,
520	   typename _BinaryPredicate>
521    _ForwardIterator1
522    __find_end(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
523	       _ForwardIterator2 __first2, _ForwardIterator2 __last2,
524	       forward_iterator_tag, forward_iterator_tag,
525	       _BinaryPredicate __comp)
526    {
527      if (__first2 == __last2)
528	return __last1;
529      else
530	{
531	  _ForwardIterator1 __result = __last1;
532	  while (1)
533	    {
534	      _ForwardIterator1 __new_result
535		= _GLIBCXX_STD_A::search(__first1, __last1, __first2,
536					 __last2, __comp);
537	      if (__new_result == __last1)
538		return __result;
539	      else
540		{
541		  __result = __new_result;
542		  __first1 = __new_result;
543		  ++__first1;
544		}
545	    }
546	}
547    }
548
549  // find_end for bidirectional iterators (much faster).
550  template<typename _BidirectionalIterator1, typename _BidirectionalIterator2>
551    _BidirectionalIterator1
552    __find_end(_BidirectionalIterator1 __first1,
553	       _BidirectionalIterator1 __last1,
554	       _BidirectionalIterator2 __first2,
555	       _BidirectionalIterator2 __last2,
556	       bidirectional_iterator_tag, bidirectional_iterator_tag)
557    {
558      // concept requirements
559      __glibcxx_function_requires(_BidirectionalIteratorConcept<
560				  _BidirectionalIterator1>)
561      __glibcxx_function_requires(_BidirectionalIteratorConcept<
562				  _BidirectionalIterator2>)
563
564      typedef reverse_iterator<_BidirectionalIterator1> _RevIterator1;
565      typedef reverse_iterator<_BidirectionalIterator2> _RevIterator2;
566
567      _RevIterator1 __rlast1(__first1);
568      _RevIterator2 __rlast2(__first2);
569      _RevIterator1 __rresult = _GLIBCXX_STD_A::search(_RevIterator1(__last1),
570						       __rlast1,
571						       _RevIterator2(__last2),
572						       __rlast2);
573
574      if (__rresult == __rlast1)
575	return __last1;
576      else
577	{
578	  _BidirectionalIterator1 __result = __rresult.base();
579	  std::advance(__result, -std::distance(__first2, __last2));
580	  return __result;
581	}
582    }
583
584  template<typename _BidirectionalIterator1, typename _BidirectionalIterator2,
585	   typename _BinaryPredicate>
586    _BidirectionalIterator1
587    __find_end(_BidirectionalIterator1 __first1,
588	       _BidirectionalIterator1 __last1,
589	       _BidirectionalIterator2 __first2,
590	       _BidirectionalIterator2 __last2,
591	       bidirectional_iterator_tag, bidirectional_iterator_tag,
592	       _BinaryPredicate __comp)
593    {
594      // concept requirements
595      __glibcxx_function_requires(_BidirectionalIteratorConcept<
596				  _BidirectionalIterator1>)
597      __glibcxx_function_requires(_BidirectionalIteratorConcept<
598				  _BidirectionalIterator2>)
599
600      typedef reverse_iterator<_BidirectionalIterator1> _RevIterator1;
601      typedef reverse_iterator<_BidirectionalIterator2> _RevIterator2;
602
603      _RevIterator1 __rlast1(__first1);
604      _RevIterator2 __rlast2(__first2);
605      _RevIterator1 __rresult = std::search(_RevIterator1(__last1), __rlast1,
606					    _RevIterator2(__last2), __rlast2,
607					    __comp);
608
609      if (__rresult == __rlast1)
610	return __last1;
611      else
612	{
613	  _BidirectionalIterator1 __result = __rresult.base();
614	  std::advance(__result, -std::distance(__first2, __last2));
615	  return __result;
616	}
617    }
618
619  /**
620   *  @brief  Find last matching subsequence in a sequence.
621   *  @ingroup non_mutating_algorithms
622   *  @param  __first1  Start of range to search.
623   *  @param  __last1   End of range to search.
624   *  @param  __first2  Start of sequence to match.
625   *  @param  __last2   End of sequence to match.
626   *  @return   The last iterator @c i in the range
627   *  @p [__first1,__last1-(__last2-__first2)) such that @c *(i+N) ==
628   *  @p *(__first2+N) for each @c N in the range @p
629   *  [0,__last2-__first2), or @p __last1 if no such iterator exists.
630   *
631   *  Searches the range @p [__first1,__last1) for a sub-sequence that
632   *  compares equal value-by-value with the sequence given by @p
633   *  [__first2,__last2) and returns an iterator to the __first
634   *  element of the sub-sequence, or @p __last1 if the sub-sequence
635   *  is not found.  The sub-sequence will be the last such
636   *  subsequence contained in [__first,__last1).
637   *
638   *  Because the sub-sequence must lie completely within the range @p
639   *  [__first1,__last1) it must start at a position less than @p
640   *  __last1-(__last2-__first2) where @p __last2-__first2 is the
641   *  length of the sub-sequence.  This means that the returned
642   *  iterator @c i will be in the range @p
643   *  [__first1,__last1-(__last2-__first2))
644  */
645  template<typename _ForwardIterator1, typename _ForwardIterator2>
646    inline _ForwardIterator1
647    find_end(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
648	     _ForwardIterator2 __first2, _ForwardIterator2 __last2)
649    {
650      // concept requirements
651      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator1>)
652      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator2>)
653      __glibcxx_function_requires(_EqualOpConcept<
654	    typename iterator_traits<_ForwardIterator1>::value_type,
655	    typename iterator_traits<_ForwardIterator2>::value_type>)
656      __glibcxx_requires_valid_range(__first1, __last1);
657      __glibcxx_requires_valid_range(__first2, __last2);
658
659      return std::__find_end(__first1, __last1, __first2, __last2,
660			     std::__iterator_category(__first1),
661			     std::__iterator_category(__first2));
662    }
663
664  /**
665   *  @brief  Find last matching subsequence in a sequence using a predicate.
666   *  @ingroup non_mutating_algorithms
667   *  @param  __first1  Start of range to search.
668   *  @param  __last1   End of range to search.
669   *  @param  __first2  Start of sequence to match.
670   *  @param  __last2   End of sequence to match.
671   *  @param  __comp    The predicate to use.
672   *  @return The last iterator @c i in the range @p
673   *  [__first1,__last1-(__last2-__first2)) such that @c
674   *  predicate(*(i+N), @p (__first2+N)) is true for each @c N in the
675   *  range @p [0,__last2-__first2), or @p __last1 if no such iterator
676   *  exists.
677   *
678   *  Searches the range @p [__first1,__last1) for a sub-sequence that
679   *  compares equal value-by-value with the sequence given by @p
680   *  [__first2,__last2) using comp as a predicate and returns an
681   *  iterator to the first element of the sub-sequence, or @p __last1
682   *  if the sub-sequence is not found.  The sub-sequence will be the
683   *  last such subsequence contained in [__first,__last1).
684   *
685   *  Because the sub-sequence must lie completely within the range @p
686   *  [__first1,__last1) it must start at a position less than @p
687   *  __last1-(__last2-__first2) where @p __last2-__first2 is the
688   *  length of the sub-sequence.  This means that the returned
689   *  iterator @c i will be in the range @p
690   *  [__first1,__last1-(__last2-__first2))
691  */
692  template<typename _ForwardIterator1, typename _ForwardIterator2,
693	   typename _BinaryPredicate>
694    inline _ForwardIterator1
695    find_end(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
696	     _ForwardIterator2 __first2, _ForwardIterator2 __last2,
697	     _BinaryPredicate __comp)
698    {
699      // concept requirements
700      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator1>)
701      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator2>)
702      __glibcxx_function_requires(_BinaryPredicateConcept<_BinaryPredicate,
703	    typename iterator_traits<_ForwardIterator1>::value_type,
704	    typename iterator_traits<_ForwardIterator2>::value_type>)
705      __glibcxx_requires_valid_range(__first1, __last1);
706      __glibcxx_requires_valid_range(__first2, __last2);
707
708      return std::__find_end(__first1, __last1, __first2, __last2,
709			     std::__iterator_category(__first1),
710			     std::__iterator_category(__first2),
711			     __comp);
712    }
713
714#if __cplusplus >= 201103L
715  /**
716   *  @brief  Checks that a predicate is true for all the elements
717   *          of a sequence.
718   *  @ingroup non_mutating_algorithms
719   *  @param  __first   An input iterator.
720   *  @param  __last    An input iterator.
721   *  @param  __pred    A predicate.
722   *  @return  True if the check is true, false otherwise.
723   *
724   *  Returns true if @p __pred is true for each element in the range
725   *  @p [__first,__last), and false otherwise.
726  */
727  template<typename _InputIterator, typename _Predicate>
728    inline bool
729    all_of(_InputIterator __first, _InputIterator __last, _Predicate __pred)
730    { return __last == std::find_if_not(__first, __last, __pred); }
731
732  /**
733   *  @brief  Checks that a predicate is false for all the elements
734   *          of a sequence.
735   *  @ingroup non_mutating_algorithms
736   *  @param  __first   An input iterator.
737   *  @param  __last    An input iterator.
738   *  @param  __pred    A predicate.
739   *  @return  True if the check is true, false otherwise.
740   *
741   *  Returns true if @p __pred is false for each element in the range
742   *  @p [__first,__last), and false otherwise.
743  */
744  template<typename _InputIterator, typename _Predicate>
745    inline bool
746    none_of(_InputIterator __first, _InputIterator __last, _Predicate __pred)
747    { return __last == _GLIBCXX_STD_A::find_if(__first, __last, __pred); }
748
749  /**
750   *  @brief  Checks that a predicate is false for at least an element
751   *          of a sequence.
752   *  @ingroup non_mutating_algorithms
753   *  @param  __first   An input iterator.
754   *  @param  __last    An input iterator.
755   *  @param  __pred    A predicate.
756   *  @return  True if the check is true, false otherwise.
757   *
758   *  Returns true if an element exists in the range @p
759   *  [__first,__last) such that @p __pred is true, and false
760   *  otherwise.
761  */
762  template<typename _InputIterator, typename _Predicate>
763    inline bool
764    any_of(_InputIterator __first, _InputIterator __last, _Predicate __pred)
765    { return !std::none_of(__first, __last, __pred); }
766
767  /**
768   *  @brief  Find the first element in a sequence for which a
769   *          predicate is false.
770   *  @ingroup non_mutating_algorithms
771   *  @param  __first  An input iterator.
772   *  @param  __last   An input iterator.
773   *  @param  __pred   A predicate.
774   *  @return   The first iterator @c i in the range @p [__first,__last)
775   *  such that @p __pred(*i) is false, or @p __last if no such iterator exists.
776  */
777  template<typename _InputIterator, typename _Predicate>
778    inline _InputIterator
779    find_if_not(_InputIterator __first, _InputIterator __last,
780		_Predicate __pred)
781    {
782      // concept requirements
783      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
784      __glibcxx_function_requires(_UnaryPredicateConcept<_Predicate,
785	      typename iterator_traits<_InputIterator>::value_type>)
786      __glibcxx_requires_valid_range(__first, __last);
787      return std::__find_if_not(__first, __last, __pred);
788    }
789
790  /**
791   *  @brief  Checks whether the sequence is partitioned.
792   *  @ingroup mutating_algorithms
793   *  @param  __first  An input iterator.
794   *  @param  __last   An input iterator.
795   *  @param  __pred   A predicate.
796   *  @return  True if the range @p [__first,__last) is partioned by @p __pred,
797   *  i.e. if all elements that satisfy @p __pred appear before those that
798   *  do not.
799  */
800  template<typename _InputIterator, typename _Predicate>
801    inline bool
802    is_partitioned(_InputIterator __first, _InputIterator __last,
803		   _Predicate __pred)
804    {
805      __first = std::find_if_not(__first, __last, __pred);
806      return std::none_of(__first, __last, __pred);
807    }
808
809  /**
810   *  @brief  Find the partition point of a partitioned range.
811   *  @ingroup mutating_algorithms
812   *  @param  __first   An iterator.
813   *  @param  __last    Another iterator.
814   *  @param  __pred    A predicate.
815   *  @return  An iterator @p mid such that @p all_of(__first, mid, __pred)
816   *           and @p none_of(mid, __last, __pred) are both true.
817  */
818  template<typename _ForwardIterator, typename _Predicate>
819    _ForwardIterator
820    partition_point(_ForwardIterator __first, _ForwardIterator __last,
821		    _Predicate __pred)
822    {
823      // concept requirements
824      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
825      __glibcxx_function_requires(_UnaryPredicateConcept<_Predicate,
826	      typename iterator_traits<_ForwardIterator>::value_type>)
827
828      // A specific debug-mode test will be necessary...
829      __glibcxx_requires_valid_range(__first, __last);
830
831      typedef typename iterator_traits<_ForwardIterator>::difference_type
832	_DistanceType;
833
834      _DistanceType __len = std::distance(__first, __last);
835      _DistanceType __half;
836      _ForwardIterator __middle;
837
838      while (__len > 0)
839	{
840	  __half = __len >> 1;
841	  __middle = __first;
842	  std::advance(__middle, __half);
843	  if (__pred(*__middle))
844	    {
845	      __first = __middle;
846	      ++__first;
847	      __len = __len - __half - 1;
848	    }
849	  else
850	    __len = __half;
851	}
852      return __first;
853    }
854#endif
855
856
857  /**
858   *  @brief Copy a sequence, removing elements of a given value.
859   *  @ingroup mutating_algorithms
860   *  @param  __first   An input iterator.
861   *  @param  __last    An input iterator.
862   *  @param  __result  An output iterator.
863   *  @param  __value   The value to be removed.
864   *  @return   An iterator designating the end of the resulting sequence.
865   *
866   *  Copies each element in the range @p [__first,__last) not equal
867   *  to @p __value to the range beginning at @p __result.
868   *  remove_copy() is stable, so the relative order of elements that
869   *  are copied is unchanged.
870  */
871  template<typename _InputIterator, typename _OutputIterator, typename _Tp>
872    _OutputIterator
873    remove_copy(_InputIterator __first, _InputIterator __last,
874		_OutputIterator __result, const _Tp& __value)
875    {
876      // concept requirements
877      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
878      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
879	    typename iterator_traits<_InputIterator>::value_type>)
880      __glibcxx_function_requires(_EqualOpConcept<
881	    typename iterator_traits<_InputIterator>::value_type, _Tp>)
882      __glibcxx_requires_valid_range(__first, __last);
883
884      for (; __first != __last; ++__first)
885	if (!(*__first == __value))
886	  {
887	    *__result = *__first;
888	    ++__result;
889	  }
890      return __result;
891    }
892
893  /**
894   *  @brief Copy a sequence, removing elements for which a predicate is true.
895   *  @ingroup mutating_algorithms
896   *  @param  __first   An input iterator.
897   *  @param  __last    An input iterator.
898   *  @param  __result  An output iterator.
899   *  @param  __pred    A predicate.
900   *  @return   An iterator designating the end of the resulting sequence.
901   *
902   *  Copies each element in the range @p [__first,__last) for which
903   *  @p __pred returns false to the range beginning at @p __result.
904   *
905   *  remove_copy_if() is stable, so the relative order of elements that are
906   *  copied is unchanged.
907  */
908  template<typename _InputIterator, typename _OutputIterator,
909	   typename _Predicate>
910    _OutputIterator
911    remove_copy_if(_InputIterator __first, _InputIterator __last,
912		   _OutputIterator __result, _Predicate __pred)
913    {
914      // concept requirements
915      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
916      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
917	    typename iterator_traits<_InputIterator>::value_type>)
918      __glibcxx_function_requires(_UnaryPredicateConcept<_Predicate,
919	    typename iterator_traits<_InputIterator>::value_type>)
920      __glibcxx_requires_valid_range(__first, __last);
921
922      for (; __first != __last; ++__first)
923	if (!bool(__pred(*__first)))
924	  {
925	    *__result = *__first;
926	    ++__result;
927	  }
928      return __result;
929    }
930
931#if __cplusplus >= 201103L
932  /**
933   *  @brief Copy the elements of a sequence for which a predicate is true.
934   *  @ingroup mutating_algorithms
935   *  @param  __first   An input iterator.
936   *  @param  __last    An input iterator.
937   *  @param  __result  An output iterator.
938   *  @param  __pred    A predicate.
939   *  @return   An iterator designating the end of the resulting sequence.
940   *
941   *  Copies each element in the range @p [__first,__last) for which
942   *  @p __pred returns true to the range beginning at @p __result.
943   *
944   *  copy_if() is stable, so the relative order of elements that are
945   *  copied is unchanged.
946  */
947  template<typename _InputIterator, typename _OutputIterator,
948	   typename _Predicate>
949    _OutputIterator
950    copy_if(_InputIterator __first, _InputIterator __last,
951	    _OutputIterator __result, _Predicate __pred)
952    {
953      // concept requirements
954      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
955      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
956	    typename iterator_traits<_InputIterator>::value_type>)
957      __glibcxx_function_requires(_UnaryPredicateConcept<_Predicate,
958	    typename iterator_traits<_InputIterator>::value_type>)
959      __glibcxx_requires_valid_range(__first, __last);
960
961      for (; __first != __last; ++__first)
962	if (__pred(*__first))
963	  {
964	    *__result = *__first;
965	    ++__result;
966	  }
967      return __result;
968    }
969
970
971  template<typename _InputIterator, typename _Size, typename _OutputIterator>
972    _OutputIterator
973    __copy_n(_InputIterator __first, _Size __n,
974	     _OutputIterator __result, input_iterator_tag)
975    {
976      if (__n > 0)
977	{
978	  while (true)
979	    {
980	      *__result = *__first;
981	      ++__result;
982	      if (--__n > 0)
983		++__first;
984	      else
985		break;
986	    }
987	}
988      return __result;
989    }
990
991  template<typename _RandomAccessIterator, typename _Size,
992	   typename _OutputIterator>
993    inline _OutputIterator
994    __copy_n(_RandomAccessIterator __first, _Size __n,
995	     _OutputIterator __result, random_access_iterator_tag)
996    { return std::copy(__first, __first + __n, __result); }
997
998  /**
999   *  @brief Copies the range [first,first+n) into [result,result+n).
1000   *  @ingroup mutating_algorithms
1001   *  @param  __first  An input iterator.
1002   *  @param  __n      The number of elements to copy.
1003   *  @param  __result An output iterator.
1004   *  @return  result+n.
1005   *
1006   *  This inline function will boil down to a call to @c memmove whenever
1007   *  possible.  Failing that, if random access iterators are passed, then the
1008   *  loop count will be known (and therefore a candidate for compiler
1009   *  optimizations such as unrolling).
1010  */
1011  template<typename _InputIterator, typename _Size, typename _OutputIterator>
1012    inline _OutputIterator
1013    copy_n(_InputIterator __first, _Size __n, _OutputIterator __result)
1014    {
1015      // concept requirements
1016      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
1017      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
1018	    typename iterator_traits<_InputIterator>::value_type>)
1019
1020      return std::__copy_n(__first, __n, __result,
1021			   std::__iterator_category(__first));
1022    }
1023
1024  /**
1025   *  @brief Copy the elements of a sequence to separate output sequences
1026   *         depending on the truth value of a predicate.
1027   *  @ingroup mutating_algorithms
1028   *  @param  __first   An input iterator.
1029   *  @param  __last    An input iterator.
1030   *  @param  __out_true   An output iterator.
1031   *  @param  __out_false  An output iterator.
1032   *  @param  __pred    A predicate.
1033   *  @return   A pair designating the ends of the resulting sequences.
1034   *
1035   *  Copies each element in the range @p [__first,__last) for which
1036   *  @p __pred returns true to the range beginning at @p out_true
1037   *  and each element for which @p __pred returns false to @p __out_false.
1038  */
1039  template<typename _InputIterator, typename _OutputIterator1,
1040	   typename _OutputIterator2, typename _Predicate>
1041    pair<_OutputIterator1, _OutputIterator2>
1042    partition_copy(_InputIterator __first, _InputIterator __last,
1043		   _OutputIterator1 __out_true, _OutputIterator2 __out_false,
1044		   _Predicate __pred)
1045    {
1046      // concept requirements
1047      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
1048      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator1,
1049	    typename iterator_traits<_InputIterator>::value_type>)
1050      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator2,
1051	    typename iterator_traits<_InputIterator>::value_type>)
1052      __glibcxx_function_requires(_UnaryPredicateConcept<_Predicate,
1053	    typename iterator_traits<_InputIterator>::value_type>)
1054      __glibcxx_requires_valid_range(__first, __last);
1055
1056      for (; __first != __last; ++__first)
1057	if (__pred(*__first))
1058	  {
1059	    *__out_true = *__first;
1060	    ++__out_true;
1061	  }
1062	else
1063	  {
1064	    *__out_false = *__first;
1065	    ++__out_false;
1066	  }
1067
1068      return pair<_OutputIterator1, _OutputIterator2>(__out_true, __out_false);
1069    }
1070#endif
1071
1072  /**
1073   *  @brief Remove elements from a sequence.
1074   *  @ingroup mutating_algorithms
1075   *  @param  __first  An input iterator.
1076   *  @param  __last   An input iterator.
1077   *  @param  __value  The value to be removed.
1078   *  @return   An iterator designating the end of the resulting sequence.
1079   *
1080   *  All elements equal to @p __value are removed from the range
1081   *  @p [__first,__last).
1082   *
1083   *  remove() is stable, so the relative order of elements that are
1084   *  not removed is unchanged.
1085   *
1086   *  Elements between the end of the resulting sequence and @p __last
1087   *  are still present, but their value is unspecified.
1088  */
1089  template<typename _ForwardIterator, typename _Tp>
1090    _ForwardIterator
1091    remove(_ForwardIterator __first, _ForwardIterator __last,
1092	   const _Tp& __value)
1093    {
1094      // concept requirements
1095      __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<
1096				  _ForwardIterator>)
1097      __glibcxx_function_requires(_EqualOpConcept<
1098	    typename iterator_traits<_ForwardIterator>::value_type, _Tp>)
1099      __glibcxx_requires_valid_range(__first, __last);
1100
1101      __first = _GLIBCXX_STD_A::find(__first, __last, __value);
1102      if(__first == __last)
1103        return __first;
1104      _ForwardIterator __result = __first;
1105      ++__first;
1106      for(; __first != __last; ++__first)
1107        if(!(*__first == __value))
1108          {
1109            *__result = _GLIBCXX_MOVE(*__first);
1110            ++__result;
1111          }
1112      return __result;
1113    }
1114
1115  /**
1116   *  @brief Remove elements from a sequence using a predicate.
1117   *  @ingroup mutating_algorithms
1118   *  @param  __first  A forward iterator.
1119   *  @param  __last   A forward iterator.
1120   *  @param  __pred   A predicate.
1121   *  @return   An iterator designating the end of the resulting sequence.
1122   *
1123   *  All elements for which @p __pred returns true are removed from the range
1124   *  @p [__first,__last).
1125   *
1126   *  remove_if() is stable, so the relative order of elements that are
1127   *  not removed is unchanged.
1128   *
1129   *  Elements between the end of the resulting sequence and @p __last
1130   *  are still present, but their value is unspecified.
1131  */
1132  template<typename _ForwardIterator, typename _Predicate>
1133    _ForwardIterator
1134    remove_if(_ForwardIterator __first, _ForwardIterator __last,
1135	      _Predicate __pred)
1136    {
1137      // concept requirements
1138      __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<
1139				  _ForwardIterator>)
1140      __glibcxx_function_requires(_UnaryPredicateConcept<_Predicate,
1141	    typename iterator_traits<_ForwardIterator>::value_type>)
1142      __glibcxx_requires_valid_range(__first, __last);
1143
1144      __first = _GLIBCXX_STD_A::find_if(__first, __last, __pred);
1145      if(__first == __last)
1146        return __first;
1147      _ForwardIterator __result = __first;
1148      ++__first;
1149      for(; __first != __last; ++__first)
1150        if(!bool(__pred(*__first)))
1151          {
1152            *__result = _GLIBCXX_MOVE(*__first);
1153            ++__result;
1154          }
1155      return __result;
1156    }
1157
1158  /**
1159   *  @brief Remove consecutive duplicate values from a sequence.
1160   *  @ingroup mutating_algorithms
1161   *  @param  __first  A forward iterator.
1162   *  @param  __last   A forward iterator.
1163   *  @return  An iterator designating the end of the resulting sequence.
1164   *
1165   *  Removes all but the first element from each group of consecutive
1166   *  values that compare equal.
1167   *  unique() is stable, so the relative order of elements that are
1168   *  not removed is unchanged.
1169   *  Elements between the end of the resulting sequence and @p __last
1170   *  are still present, but their value is unspecified.
1171  */
1172  template<typename _ForwardIterator>
1173    _ForwardIterator
1174    unique(_ForwardIterator __first, _ForwardIterator __last)
1175    {
1176      // concept requirements
1177      __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<
1178				  _ForwardIterator>)
1179      __glibcxx_function_requires(_EqualityComparableConcept<
1180		     typename iterator_traits<_ForwardIterator>::value_type>)
1181      __glibcxx_requires_valid_range(__first, __last);
1182
1183      // Skip the beginning, if already unique.
1184      __first = _GLIBCXX_STD_A::adjacent_find(__first, __last);
1185      if (__first == __last)
1186	return __last;
1187
1188      // Do the real copy work.
1189      _ForwardIterator __dest = __first;
1190      ++__first;
1191      while (++__first != __last)
1192	if (!(*__dest == *__first))
1193	  *++__dest = _GLIBCXX_MOVE(*__first);
1194      return ++__dest;
1195    }
1196
1197  /**
1198   *  @brief Remove consecutive values from a sequence using a predicate.
1199   *  @ingroup mutating_algorithms
1200   *  @param  __first        A forward iterator.
1201   *  @param  __last         A forward iterator.
1202   *  @param  __binary_pred  A binary predicate.
1203   *  @return  An iterator designating the end of the resulting sequence.
1204   *
1205   *  Removes all but the first element from each group of consecutive
1206   *  values for which @p __binary_pred returns true.
1207   *  unique() is stable, so the relative order of elements that are
1208   *  not removed is unchanged.
1209   *  Elements between the end of the resulting sequence and @p __last
1210   *  are still present, but their value is unspecified.
1211  */
1212  template<typename _ForwardIterator, typename _BinaryPredicate>
1213    _ForwardIterator
1214    unique(_ForwardIterator __first, _ForwardIterator __last,
1215           _BinaryPredicate __binary_pred)
1216    {
1217      // concept requirements
1218      __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<
1219				  _ForwardIterator>)
1220      __glibcxx_function_requires(_BinaryPredicateConcept<_BinaryPredicate,
1221		typename iterator_traits<_ForwardIterator>::value_type,
1222		typename iterator_traits<_ForwardIterator>::value_type>)
1223      __glibcxx_requires_valid_range(__first, __last);
1224
1225      // Skip the beginning, if already unique.
1226      __first = _GLIBCXX_STD_A::adjacent_find(__first, __last, __binary_pred);
1227      if (__first == __last)
1228	return __last;
1229
1230      // Do the real copy work.
1231      _ForwardIterator __dest = __first;
1232      ++__first;
1233      while (++__first != __last)
1234	if (!bool(__binary_pred(*__dest, *__first)))
1235	  *++__dest = _GLIBCXX_MOVE(*__first);
1236      return ++__dest;
1237    }
1238
1239  /**
1240   *  This is an uglified unique_copy(_InputIterator, _InputIterator,
1241   *                                  _OutputIterator)
1242   *  overloaded for forward iterators and output iterator as result.
1243  */
1244  template<typename _ForwardIterator, typename _OutputIterator>
1245    _OutputIterator
1246    __unique_copy(_ForwardIterator __first, _ForwardIterator __last,
1247		  _OutputIterator __result,
1248		  forward_iterator_tag, output_iterator_tag)
1249    {
1250      // concept requirements -- taken care of in dispatching function
1251      _ForwardIterator __next = __first;
1252      *__result = *__first;
1253      while (++__next != __last)
1254	if (!(*__first == *__next))
1255	  {
1256	    __first = __next;
1257	    *++__result = *__first;
1258	  }
1259      return ++__result;
1260    }
1261
1262  /**
1263   *  This is an uglified unique_copy(_InputIterator, _InputIterator,
1264   *                                  _OutputIterator)
1265   *  overloaded for input iterators and output iterator as result.
1266  */
1267  template<typename _InputIterator, typename _OutputIterator>
1268    _OutputIterator
1269    __unique_copy(_InputIterator __first, _InputIterator __last,
1270		  _OutputIterator __result,
1271		  input_iterator_tag, output_iterator_tag)
1272    {
1273      // concept requirements -- taken care of in dispatching function
1274      typename iterator_traits<_InputIterator>::value_type __value = *__first;
1275      *__result = __value;
1276      while (++__first != __last)
1277	if (!(__value == *__first))
1278	  {
1279	    __value = *__first;
1280	    *++__result = __value;
1281	  }
1282      return ++__result;
1283    }
1284
1285  /**
1286   *  This is an uglified unique_copy(_InputIterator, _InputIterator,
1287   *                                  _OutputIterator)
1288   *  overloaded for input iterators and forward iterator as result.
1289  */
1290  template<typename _InputIterator, typename _ForwardIterator>
1291    _ForwardIterator
1292    __unique_copy(_InputIterator __first, _InputIterator __last,
1293		  _ForwardIterator __result,
1294		  input_iterator_tag, forward_iterator_tag)
1295    {
1296      // concept requirements -- taken care of in dispatching function
1297      *__result = *__first;
1298      while (++__first != __last)
1299	if (!(*__result == *__first))
1300	  *++__result = *__first;
1301      return ++__result;
1302    }
1303
1304  /**
1305   *  This is an uglified
1306   *  unique_copy(_InputIterator, _InputIterator, _OutputIterator,
1307   *              _BinaryPredicate)
1308   *  overloaded for forward iterators and output iterator as result.
1309  */
1310  template<typename _ForwardIterator, typename _OutputIterator,
1311	   typename _BinaryPredicate>
1312    _OutputIterator
1313    __unique_copy(_ForwardIterator __first, _ForwardIterator __last,
1314		  _OutputIterator __result, _BinaryPredicate __binary_pred,
1315		  forward_iterator_tag, output_iterator_tag)
1316    {
1317      // concept requirements -- iterators already checked
1318      __glibcxx_function_requires(_BinaryPredicateConcept<_BinaryPredicate,
1319	  typename iterator_traits<_ForwardIterator>::value_type,
1320	  typename iterator_traits<_ForwardIterator>::value_type>)
1321
1322      _ForwardIterator __next = __first;
1323      *__result = *__first;
1324      while (++__next != __last)
1325	if (!bool(__binary_pred(*__first, *__next)))
1326	  {
1327	    __first = __next;
1328	    *++__result = *__first;
1329	  }
1330      return ++__result;
1331    }
1332
1333  /**
1334   *  This is an uglified
1335   *  unique_copy(_InputIterator, _InputIterator, _OutputIterator,
1336   *              _BinaryPredicate)
1337   *  overloaded for input iterators and output iterator as result.
1338  */
1339  template<typename _InputIterator, typename _OutputIterator,
1340	   typename _BinaryPredicate>
1341    _OutputIterator
1342    __unique_copy(_InputIterator __first, _InputIterator __last,
1343		  _OutputIterator __result, _BinaryPredicate __binary_pred,
1344		  input_iterator_tag, output_iterator_tag)
1345    {
1346      // concept requirements -- iterators already checked
1347      __glibcxx_function_requires(_BinaryPredicateConcept<_BinaryPredicate,
1348	  typename iterator_traits<_InputIterator>::value_type,
1349	  typename iterator_traits<_InputIterator>::value_type>)
1350
1351      typename iterator_traits<_InputIterator>::value_type __value = *__first;
1352      *__result = __value;
1353      while (++__first != __last)
1354	if (!bool(__binary_pred(__value, *__first)))
1355	  {
1356	    __value = *__first;
1357	    *++__result = __value;
1358	  }
1359      return ++__result;
1360    }
1361
1362  /**
1363   *  This is an uglified
1364   *  unique_copy(_InputIterator, _InputIterator, _OutputIterator,
1365   *              _BinaryPredicate)
1366   *  overloaded for input iterators and forward iterator as result.
1367  */
1368  template<typename _InputIterator, typename _ForwardIterator,
1369	   typename _BinaryPredicate>
1370    _ForwardIterator
1371    __unique_copy(_InputIterator __first, _InputIterator __last,
1372		  _ForwardIterator __result, _BinaryPredicate __binary_pred,
1373		  input_iterator_tag, forward_iterator_tag)
1374    {
1375      // concept requirements -- iterators already checked
1376      __glibcxx_function_requires(_BinaryPredicateConcept<_BinaryPredicate,
1377	  typename iterator_traits<_ForwardIterator>::value_type,
1378	  typename iterator_traits<_InputIterator>::value_type>)
1379
1380      *__result = *__first;
1381      while (++__first != __last)
1382	if (!bool(__binary_pred(*__result, *__first)))
1383	  *++__result = *__first;
1384      return ++__result;
1385    }
1386
1387  /**
1388   *  This is an uglified reverse(_BidirectionalIterator,
1389   *                              _BidirectionalIterator)
1390   *  overloaded for bidirectional iterators.
1391  */
1392  template<typename _BidirectionalIterator>
1393    void
1394    __reverse(_BidirectionalIterator __first, _BidirectionalIterator __last,
1395	      bidirectional_iterator_tag)
1396    {
1397      while (true)
1398	if (__first == __last || __first == --__last)
1399	  return;
1400	else
1401	  {
1402	    std::iter_swap(__first, __last);
1403	    ++__first;
1404	  }
1405    }
1406
1407  /**
1408   *  This is an uglified reverse(_BidirectionalIterator,
1409   *                              _BidirectionalIterator)
1410   *  overloaded for random access iterators.
1411  */
1412  template<typename _RandomAccessIterator>
1413    void
1414    __reverse(_RandomAccessIterator __first, _RandomAccessIterator __last,
1415	      random_access_iterator_tag)
1416    {
1417      if (__first == __last)
1418	return;
1419      --__last;
1420      while (__first < __last)
1421	{
1422	  std::iter_swap(__first, __last);
1423	  ++__first;
1424	  --__last;
1425	}
1426    }
1427
1428  /**
1429   *  @brief Reverse a sequence.
1430   *  @ingroup mutating_algorithms
1431   *  @param  __first  A bidirectional iterator.
1432   *  @param  __last   A bidirectional iterator.
1433   *  @return   reverse() returns no value.
1434   *
1435   *  Reverses the order of the elements in the range @p [__first,__last),
1436   *  so that the first element becomes the last etc.
1437   *  For every @c i such that @p 0<=i<=(__last-__first)/2), @p reverse()
1438   *  swaps @p *(__first+i) and @p *(__last-(i+1))
1439  */
1440  template<typename _BidirectionalIterator>
1441    inline void
1442    reverse(_BidirectionalIterator __first, _BidirectionalIterator __last)
1443    {
1444      // concept requirements
1445      __glibcxx_function_requires(_Mutable_BidirectionalIteratorConcept<
1446				  _BidirectionalIterator>)
1447      __glibcxx_requires_valid_range(__first, __last);
1448      std::__reverse(__first, __last, std::__iterator_category(__first));
1449    }
1450
1451  /**
1452   *  @brief Copy a sequence, reversing its elements.
1453   *  @ingroup mutating_algorithms
1454   *  @param  __first   A bidirectional iterator.
1455   *  @param  __last    A bidirectional iterator.
1456   *  @param  __result  An output iterator.
1457   *  @return  An iterator designating the end of the resulting sequence.
1458   *
1459   *  Copies the elements in the range @p [__first,__last) to the
1460   *  range @p [__result,__result+(__last-__first)) such that the
1461   *  order of the elements is reversed.  For every @c i such that @p
1462   *  0<=i<=(__last-__first), @p reverse_copy() performs the
1463   *  assignment @p *(__result+(__last-__first)-1-i) = *(__first+i).
1464   *  The ranges @p [__first,__last) and @p
1465   *  [__result,__result+(__last-__first)) must not overlap.
1466  */
1467  template<typename _BidirectionalIterator, typename _OutputIterator>
1468    _OutputIterator
1469    reverse_copy(_BidirectionalIterator __first, _BidirectionalIterator __last,
1470		 _OutputIterator __result)
1471    {
1472      // concept requirements
1473      __glibcxx_function_requires(_BidirectionalIteratorConcept<
1474				  _BidirectionalIterator>)
1475      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
1476		typename iterator_traits<_BidirectionalIterator>::value_type>)
1477      __glibcxx_requires_valid_range(__first, __last);
1478
1479      while (__first != __last)
1480	{
1481	  --__last;
1482	  *__result = *__last;
1483	  ++__result;
1484	}
1485      return __result;
1486    }
1487
1488  /**
1489   *  This is a helper function for the rotate algorithm specialized on RAIs.
1490   *  It returns the greatest common divisor of two integer values.
1491  */
1492  template<typename _EuclideanRingElement>
1493    _EuclideanRingElement
1494    __gcd(_EuclideanRingElement __m, _EuclideanRingElement __n)
1495    {
1496      while (__n != 0)
1497	{
1498	  _EuclideanRingElement __t = __m % __n;
1499	  __m = __n;
1500	  __n = __t;
1501	}
1502      return __m;
1503    }
1504
1505  /// This is a helper function for the rotate algorithm.
1506  template<typename _ForwardIterator>
1507    void
1508    __rotate(_ForwardIterator __first,
1509	     _ForwardIterator __middle,
1510	     _ForwardIterator __last,
1511	     forward_iterator_tag)
1512    {
1513      if (__first == __middle || __last  == __middle)
1514	return;
1515
1516      _ForwardIterator __first2 = __middle;
1517      do
1518	{
1519	  std::iter_swap(__first, __first2);
1520	  ++__first;
1521	  ++__first2;
1522	  if (__first == __middle)
1523	    __middle = __first2;
1524	}
1525      while (__first2 != __last);
1526
1527      __first2 = __middle;
1528
1529      while (__first2 != __last)
1530	{
1531	  std::iter_swap(__first, __first2);
1532	  ++__first;
1533	  ++__first2;
1534	  if (__first == __middle)
1535	    __middle = __first2;
1536	  else if (__first2 == __last)
1537	    __first2 = __middle;
1538	}
1539    }
1540
1541   /// This is a helper function for the rotate algorithm.
1542  template<typename _BidirectionalIterator>
1543    void
1544    __rotate(_BidirectionalIterator __first,
1545	     _BidirectionalIterator __middle,
1546	     _BidirectionalIterator __last,
1547	      bidirectional_iterator_tag)
1548    {
1549      // concept requirements
1550      __glibcxx_function_requires(_Mutable_BidirectionalIteratorConcept<
1551				  _BidirectionalIterator>)
1552
1553      if (__first == __middle || __last  == __middle)
1554	return;
1555
1556      std::__reverse(__first,  __middle, bidirectional_iterator_tag());
1557      std::__reverse(__middle, __last,   bidirectional_iterator_tag());
1558
1559      while (__first != __middle && __middle != __last)
1560	{
1561	  std::iter_swap(__first, --__last);
1562	  ++__first;
1563	}
1564
1565      if (__first == __middle)
1566	std::__reverse(__middle, __last,   bidirectional_iterator_tag());
1567      else
1568	std::__reverse(__first,  __middle, bidirectional_iterator_tag());
1569    }
1570
1571  /// This is a helper function for the rotate algorithm.
1572  template<typename _RandomAccessIterator>
1573    void
1574    __rotate(_RandomAccessIterator __first,
1575	     _RandomAccessIterator __middle,
1576	     _RandomAccessIterator __last,
1577	     random_access_iterator_tag)
1578    {
1579      // concept requirements
1580      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
1581				  _RandomAccessIterator>)
1582
1583      if (__first == __middle || __last  == __middle)
1584	return;
1585
1586      typedef typename iterator_traits<_RandomAccessIterator>::difference_type
1587	_Distance;
1588      typedef typename iterator_traits<_RandomAccessIterator>::value_type
1589	_ValueType;
1590
1591      _Distance __n = __last   - __first;
1592      _Distance __k = __middle - __first;
1593
1594      if (__k == __n - __k)
1595	{
1596	  std::swap_ranges(__first, __middle, __middle);
1597	  return;
1598	}
1599
1600      _RandomAccessIterator __p = __first;
1601
1602      for (;;)
1603	{
1604	  if (__k < __n - __k)
1605	    {
1606	      if (__is_pod(_ValueType) && __k == 1)
1607		{
1608		  _ValueType __t = _GLIBCXX_MOVE(*__p);
1609		  _GLIBCXX_MOVE3(__p + 1, __p + __n, __p);
1610		  *(__p + __n - 1) = _GLIBCXX_MOVE(__t);
1611		  return;
1612		}
1613	      _RandomAccessIterator __q = __p + __k;
1614	      for (_Distance __i = 0; __i < __n - __k; ++ __i)
1615		{
1616		  std::iter_swap(__p, __q);
1617		  ++__p;
1618		  ++__q;
1619		}
1620	      __n %= __k;
1621	      if (__n == 0)
1622		return;
1623	      std::swap(__n, __k);
1624	      __k = __n - __k;
1625	    }
1626	  else
1627	    {
1628	      __k = __n - __k;
1629	      if (__is_pod(_ValueType) && __k == 1)
1630		{
1631		  _ValueType __t = _GLIBCXX_MOVE(*(__p + __n - 1));
1632		  _GLIBCXX_MOVE_BACKWARD3(__p, __p + __n - 1, __p + __n);
1633		  *__p = _GLIBCXX_MOVE(__t);
1634		  return;
1635		}
1636	      _RandomAccessIterator __q = __p + __n;
1637	      __p = __q - __k;
1638	      for (_Distance __i = 0; __i < __n - __k; ++ __i)
1639		{
1640		  --__p;
1641		  --__q;
1642		  std::iter_swap(__p, __q);
1643		}
1644	      __n %= __k;
1645	      if (__n == 0)
1646		return;
1647	      std::swap(__n, __k);
1648	    }
1649	}
1650    }
1651
1652  /**
1653   *  @brief Rotate the elements of a sequence.
1654   *  @ingroup mutating_algorithms
1655   *  @param  __first   A forward iterator.
1656   *  @param  __middle  A forward iterator.
1657   *  @param  __last    A forward iterator.
1658   *  @return  Nothing.
1659   *
1660   *  Rotates the elements of the range @p [__first,__last) by
1661   *  @p (__middle - __first) positions so that the element at @p __middle
1662   *  is moved to @p __first, the element at @p __middle+1 is moved to
1663   *  @p __first+1 and so on for each element in the range
1664   *  @p [__first,__last).
1665   *
1666   *  This effectively swaps the ranges @p [__first,__middle) and
1667   *  @p [__middle,__last).
1668   *
1669   *  Performs
1670   *   @p *(__first+(n+(__last-__middle))%(__last-__first))=*(__first+n)
1671   *  for each @p n in the range @p [0,__last-__first).
1672  */
1673  template<typename _ForwardIterator>
1674    inline void
1675    rotate(_ForwardIterator __first, _ForwardIterator __middle,
1676	   _ForwardIterator __last)
1677    {
1678      // concept requirements
1679      __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<
1680				  _ForwardIterator>)
1681      __glibcxx_requires_valid_range(__first, __middle);
1682      __glibcxx_requires_valid_range(__middle, __last);
1683
1684      typedef typename iterator_traits<_ForwardIterator>::iterator_category
1685	_IterType;
1686      std::__rotate(__first, __middle, __last, _IterType());
1687    }
1688
1689  /**
1690   *  @brief Copy a sequence, rotating its elements.
1691   *  @ingroup mutating_algorithms
1692   *  @param  __first   A forward iterator.
1693   *  @param  __middle  A forward iterator.
1694   *  @param  __last    A forward iterator.
1695   *  @param  __result  An output iterator.
1696   *  @return   An iterator designating the end of the resulting sequence.
1697   *
1698   *  Copies the elements of the range @p [__first,__last) to the
1699   *  range beginning at @result, rotating the copied elements by
1700   *  @p (__middle-__first) positions so that the element at @p __middle
1701   *  is moved to @p __result, the element at @p __middle+1 is moved
1702   *  to @p __result+1 and so on for each element in the range @p
1703   *  [__first,__last).
1704   *
1705   *  Performs
1706   *  @p *(__result+(n+(__last-__middle))%(__last-__first))=*(__first+n)
1707   *  for each @p n in the range @p [0,__last-__first).
1708  */
1709  template<typename _ForwardIterator, typename _OutputIterator>
1710    _OutputIterator
1711    rotate_copy(_ForwardIterator __first, _ForwardIterator __middle,
1712                _ForwardIterator __last, _OutputIterator __result)
1713    {
1714      // concept requirements
1715      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
1716      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
1717		typename iterator_traits<_ForwardIterator>::value_type>)
1718      __glibcxx_requires_valid_range(__first, __middle);
1719      __glibcxx_requires_valid_range(__middle, __last);
1720
1721      return std::copy(__first, __middle,
1722                       std::copy(__middle, __last, __result));
1723    }
1724
1725  /// This is a helper function...
1726  template<typename _ForwardIterator, typename _Predicate>
1727    _ForwardIterator
1728    __partition(_ForwardIterator __first, _ForwardIterator __last,
1729		_Predicate __pred, forward_iterator_tag)
1730    {
1731      if (__first == __last)
1732	return __first;
1733
1734      while (__pred(*__first))
1735	if (++__first == __last)
1736	  return __first;
1737
1738      _ForwardIterator __next = __first;
1739
1740      while (++__next != __last)
1741	if (__pred(*__next))
1742	  {
1743	    std::iter_swap(__first, __next);
1744	    ++__first;
1745	  }
1746
1747      return __first;
1748    }
1749
1750  /// This is a helper function...
1751  template<typename _BidirectionalIterator, typename _Predicate>
1752    _BidirectionalIterator
1753    __partition(_BidirectionalIterator __first, _BidirectionalIterator __last,
1754		_Predicate __pred, bidirectional_iterator_tag)
1755    {
1756      while (true)
1757	{
1758	  while (true)
1759	    if (__first == __last)
1760	      return __first;
1761	    else if (__pred(*__first))
1762	      ++__first;
1763	    else
1764	      break;
1765	  --__last;
1766	  while (true)
1767	    if (__first == __last)
1768	      return __first;
1769	    else if (!bool(__pred(*__last)))
1770	      --__last;
1771	    else
1772	      break;
1773	  std::iter_swap(__first, __last);
1774	  ++__first;
1775	}
1776    }
1777
1778  // partition
1779
1780  /// This is a helper function...
1781  /// Requires __len != 0 and !__pred(*__first),
1782  /// same as __stable_partition_adaptive.
1783  template<typename _ForwardIterator, typename _Predicate, typename _Distance>
1784    _ForwardIterator
1785    __inplace_stable_partition(_ForwardIterator __first,
1786			       _Predicate __pred, _Distance __len)
1787    {
1788      if (__len == 1)
1789	return __first;
1790      _ForwardIterator __middle = __first;
1791      std::advance(__middle, __len / 2);
1792      _ForwardIterator __left_split =
1793	std::__inplace_stable_partition(__first, __pred, __len / 2);
1794      // Advance past true-predicate values to satisfy this
1795      // function's preconditions.
1796      _Distance __right_len = __len - __len / 2;
1797      _ForwardIterator __right_split =
1798	std::__find_if_not_n(__middle, __right_len, __pred);
1799      if (__right_len)
1800	__right_split = std::__inplace_stable_partition(__middle,
1801							__pred,
1802							__right_len);
1803      std::rotate(__left_split, __middle, __right_split);
1804      std::advance(__left_split, std::distance(__middle, __right_split));
1805      return __left_split;
1806    }
1807
1808  /// This is a helper function...
1809  /// Requires __first != __last and !__pred(*__first)
1810  /// and __len == distance(__first, __last).
1811  ///
1812  /// !__pred(*__first) allows us to guarantee that we don't
1813  /// move-assign an element onto itself.
1814  template<typename _ForwardIterator, typename _Pointer, typename _Predicate,
1815	   typename _Distance>
1816    _ForwardIterator
1817    __stable_partition_adaptive(_ForwardIterator __first,
1818				_ForwardIterator __last,
1819				_Predicate __pred, _Distance __len,
1820				_Pointer __buffer,
1821				_Distance __buffer_size)
1822    {
1823      if (__len <= __buffer_size)
1824	{
1825	  _ForwardIterator __result1 = __first;
1826	  _Pointer __result2 = __buffer;
1827	  // The precondition guarantees that !__pred(*__first), so
1828	  // move that element to the buffer before starting the loop.
1829	  // This ensures that we only call __pred once per element.
1830	  *__result2 = _GLIBCXX_MOVE(*__first);
1831	  ++__result2;
1832	  ++__first;
1833	  for (; __first != __last; ++__first)
1834	    if (__pred(*__first))
1835	      {
1836		*__result1 = _GLIBCXX_MOVE(*__first);
1837		++__result1;
1838	      }
1839	    else
1840	      {
1841		*__result2 = _GLIBCXX_MOVE(*__first);
1842		++__result2;
1843	      }
1844	  _GLIBCXX_MOVE3(__buffer, __result2, __result1);
1845	  return __result1;
1846	}
1847      else
1848	{
1849	  _ForwardIterator __middle = __first;
1850	  std::advance(__middle, __len / 2);
1851	  _ForwardIterator __left_split =
1852	    std::__stable_partition_adaptive(__first, __middle, __pred,
1853					     __len / 2, __buffer,
1854					     __buffer_size);
1855	  // Advance past true-predicate values to satisfy this
1856	  // function's preconditions.
1857	  _Distance __right_len = __len - __len / 2;
1858	  _ForwardIterator __right_split =
1859	    std::__find_if_not_n(__middle, __right_len, __pred);
1860	  if (__right_len)
1861	    __right_split =
1862	      std::__stable_partition_adaptive(__right_split, __last, __pred,
1863					       __right_len,
1864					       __buffer, __buffer_size);
1865	  std::rotate(__left_split, __middle, __right_split);
1866	  std::advance(__left_split, std::distance(__middle, __right_split));
1867	  return __left_split;
1868	}
1869    }
1870
1871  /**
1872   *  @brief Move elements for which a predicate is true to the beginning
1873   *         of a sequence, preserving relative ordering.
1874   *  @ingroup mutating_algorithms
1875   *  @param  __first   A forward iterator.
1876   *  @param  __last    A forward iterator.
1877   *  @param  __pred    A predicate functor.
1878   *  @return  An iterator @p middle such that @p __pred(i) is true for each
1879   *  iterator @p i in the range @p [first,middle) and false for each @p i
1880   *  in the range @p [middle,last).
1881   *
1882   *  Performs the same function as @p partition() with the additional
1883   *  guarantee that the relative ordering of elements in each group is
1884   *  preserved, so any two elements @p x and @p y in the range
1885   *  @p [__first,__last) such that @p __pred(x)==__pred(y) will have the same
1886   *  relative ordering after calling @p stable_partition().
1887  */
1888  template<typename _ForwardIterator, typename _Predicate>
1889    _ForwardIterator
1890    stable_partition(_ForwardIterator __first, _ForwardIterator __last,
1891		     _Predicate __pred)
1892    {
1893      // concept requirements
1894      __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<
1895				  _ForwardIterator>)
1896      __glibcxx_function_requires(_UnaryPredicateConcept<_Predicate,
1897	    typename iterator_traits<_ForwardIterator>::value_type>)
1898      __glibcxx_requires_valid_range(__first, __last);
1899
1900      __first = std::__find_if_not(__first, __last, __pred);
1901
1902      if (__first == __last)
1903	return __first;
1904      else
1905	{
1906	  typedef typename iterator_traits<_ForwardIterator>::value_type
1907	    _ValueType;
1908	  typedef typename iterator_traits<_ForwardIterator>::difference_type
1909	    _DistanceType;
1910
1911	  _Temporary_buffer<_ForwardIterator, _ValueType> __buf(__first,
1912								__last);
1913	if (__buf.size() > 0)
1914	  return
1915	    std::__stable_partition_adaptive(__first, __last, __pred,
1916					  _DistanceType(__buf.requested_size()),
1917					  __buf.begin(),
1918					  _DistanceType(__buf.size()));
1919	else
1920	  return
1921	    std::__inplace_stable_partition(__first, __pred,
1922					 _DistanceType(__buf.requested_size()));
1923	}
1924    }
1925
1926  /// This is a helper function for the sort routines.
1927  template<typename _RandomAccessIterator>
1928    void
1929    __heap_select(_RandomAccessIterator __first,
1930		  _RandomAccessIterator __middle,
1931		  _RandomAccessIterator __last)
1932    {
1933      std::make_heap(__first, __middle);
1934      for (_RandomAccessIterator __i = __middle; __i < __last; ++__i)
1935	if (*__i < *__first)
1936	  std::__pop_heap(__first, __middle, __i);
1937    }
1938
1939  /// This is a helper function for the sort routines.
1940  template<typename _RandomAccessIterator, typename _Compare>
1941    void
1942    __heap_select(_RandomAccessIterator __first,
1943		  _RandomAccessIterator __middle,
1944		  _RandomAccessIterator __last, _Compare __comp)
1945    {
1946      std::make_heap(__first, __middle, __comp);
1947      for (_RandomAccessIterator __i = __middle; __i < __last; ++__i)
1948	if (__comp(*__i, *__first))
1949	  std::__pop_heap(__first, __middle, __i, __comp);
1950    }
1951
1952  // partial_sort
1953
1954  /**
1955   *  @brief Copy the smallest elements of a sequence.
1956   *  @ingroup sorting_algorithms
1957   *  @param  __first   An iterator.
1958   *  @param  __last    Another iterator.
1959   *  @param  __result_first   A random-access iterator.
1960   *  @param  __result_last    Another random-access iterator.
1961   *  @return   An iterator indicating the end of the resulting sequence.
1962   *
1963   *  Copies and sorts the smallest N values from the range @p [__first,__last)
1964   *  to the range beginning at @p __result_first, where the number of
1965   *  elements to be copied, @p N, is the smaller of @p (__last-__first) and
1966   *  @p (__result_last-__result_first).
1967   *  After the sort if @e i and @e j are iterators in the range
1968   *  @p [__result_first,__result_first+N) such that i precedes j then
1969   *  *j<*i is false.
1970   *  The value returned is @p __result_first+N.
1971  */
1972  template<typename _InputIterator, typename _RandomAccessIterator>
1973    _RandomAccessIterator
1974    partial_sort_copy(_InputIterator __first, _InputIterator __last,
1975		      _RandomAccessIterator __result_first,
1976		      _RandomAccessIterator __result_last)
1977    {
1978      typedef typename iterator_traits<_InputIterator>::value_type
1979	_InputValueType;
1980      typedef typename iterator_traits<_RandomAccessIterator>::value_type
1981	_OutputValueType;
1982      typedef typename iterator_traits<_RandomAccessIterator>::difference_type
1983	_DistanceType;
1984
1985      // concept requirements
1986      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
1987      __glibcxx_function_requires(_ConvertibleConcept<_InputValueType,
1988				  _OutputValueType>)
1989      __glibcxx_function_requires(_LessThanOpConcept<_InputValueType,
1990				                     _OutputValueType>)
1991      __glibcxx_function_requires(_LessThanComparableConcept<_OutputValueType>)
1992      __glibcxx_requires_valid_range(__first, __last);
1993      __glibcxx_requires_valid_range(__result_first, __result_last);
1994
1995      if (__result_first == __result_last)
1996	return __result_last;
1997      _RandomAccessIterator __result_real_last = __result_first;
1998      while(__first != __last && __result_real_last != __result_last)
1999	{
2000	  *__result_real_last = *__first;
2001	  ++__result_real_last;
2002	  ++__first;
2003	}
2004      std::make_heap(__result_first, __result_real_last);
2005      while (__first != __last)
2006	{
2007	  if (*__first < *__result_first)
2008	    std::__adjust_heap(__result_first, _DistanceType(0),
2009			       _DistanceType(__result_real_last
2010					     - __result_first),
2011			       _InputValueType(*__first));
2012	  ++__first;
2013	}
2014      std::sort_heap(__result_first, __result_real_last);
2015      return __result_real_last;
2016    }
2017
2018  /**
2019   *  @brief Copy the smallest elements of a sequence using a predicate for
2020   *         comparison.
2021   *  @ingroup sorting_algorithms
2022   *  @param  __first   An input iterator.
2023   *  @param  __last    Another input iterator.
2024   *  @param  __result_first   A random-access iterator.
2025   *  @param  __result_last    Another random-access iterator.
2026   *  @param  __comp    A comparison functor.
2027   *  @return   An iterator indicating the end of the resulting sequence.
2028   *
2029   *  Copies and sorts the smallest N values from the range @p [__first,__last)
2030   *  to the range beginning at @p result_first, where the number of
2031   *  elements to be copied, @p N, is the smaller of @p (__last-__first) and
2032   *  @p (__result_last-__result_first).
2033   *  After the sort if @e i and @e j are iterators in the range
2034   *  @p [__result_first,__result_first+N) such that i precedes j then
2035   *  @p __comp(*j,*i) is false.
2036   *  The value returned is @p __result_first+N.
2037  */
2038  template<typename _InputIterator, typename _RandomAccessIterator, typename _Compare>
2039    _RandomAccessIterator
2040    partial_sort_copy(_InputIterator __first, _InputIterator __last,
2041		      _RandomAccessIterator __result_first,
2042		      _RandomAccessIterator __result_last,
2043		      _Compare __comp)
2044    {
2045      typedef typename iterator_traits<_InputIterator>::value_type
2046	_InputValueType;
2047      typedef typename iterator_traits<_RandomAccessIterator>::value_type
2048	_OutputValueType;
2049      typedef typename iterator_traits<_RandomAccessIterator>::difference_type
2050	_DistanceType;
2051
2052      // concept requirements
2053      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
2054      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
2055				  _RandomAccessIterator>)
2056      __glibcxx_function_requires(_ConvertibleConcept<_InputValueType,
2057				  _OutputValueType>)
2058      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
2059				  _InputValueType, _OutputValueType>)
2060      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
2061				  _OutputValueType, _OutputValueType>)
2062      __glibcxx_requires_valid_range(__first, __last);
2063      __glibcxx_requires_valid_range(__result_first, __result_last);
2064
2065      if (__result_first == __result_last)
2066	return __result_last;
2067      _RandomAccessIterator __result_real_last = __result_first;
2068      while(__first != __last && __result_real_last != __result_last)
2069	{
2070	  *__result_real_last = *__first;
2071	  ++__result_real_last;
2072	  ++__first;
2073	}
2074      std::make_heap(__result_first, __result_real_last, __comp);
2075      while (__first != __last)
2076	{
2077	  if (__comp(*__first, *__result_first))
2078	    std::__adjust_heap(__result_first, _DistanceType(0),
2079			       _DistanceType(__result_real_last
2080					     - __result_first),
2081			       _InputValueType(*__first),
2082			       __comp);
2083	  ++__first;
2084	}
2085      std::sort_heap(__result_first, __result_real_last, __comp);
2086      return __result_real_last;
2087    }
2088
2089  /// This is a helper function for the sort routine.
2090  template<typename _RandomAccessIterator>
2091    void
2092    __unguarded_linear_insert(_RandomAccessIterator __last)
2093    {
2094      typename iterator_traits<_RandomAccessIterator>::value_type
2095	__val = _GLIBCXX_MOVE(*__last);
2096      _RandomAccessIterator __next = __last;
2097      --__next;
2098      while (__val < *__next)
2099	{
2100	  *__last = _GLIBCXX_MOVE(*__next);
2101	  __last = __next;
2102	  --__next;
2103	}
2104      *__last = _GLIBCXX_MOVE(__val);
2105    }
2106
2107  /// This is a helper function for the sort routine.
2108  template<typename _RandomAccessIterator, typename _Compare>
2109    void
2110    __unguarded_linear_insert(_RandomAccessIterator __last,
2111			      _Compare __comp)
2112    {
2113      typename iterator_traits<_RandomAccessIterator>::value_type
2114	__val = _GLIBCXX_MOVE(*__last);
2115      _RandomAccessIterator __next = __last;
2116      --__next;
2117      while (__comp(__val, *__next))
2118	{
2119	  *__last = _GLIBCXX_MOVE(*__next);
2120	  __last = __next;
2121	  --__next;
2122	}
2123      *__last = _GLIBCXX_MOVE(__val);
2124    }
2125
2126  /// This is a helper function for the sort routine.
2127  template<typename _RandomAccessIterator>
2128    void
2129    __insertion_sort(_RandomAccessIterator __first,
2130		     _RandomAccessIterator __last)
2131    {
2132      if (__first == __last)
2133	return;
2134
2135      for (_RandomAccessIterator __i = __first + 1; __i != __last; ++__i)
2136	{
2137	  if (*__i < *__first)
2138	    {
2139	      typename iterator_traits<_RandomAccessIterator>::value_type
2140		__val = _GLIBCXX_MOVE(*__i);
2141	      _GLIBCXX_MOVE_BACKWARD3(__first, __i, __i + 1);
2142	      *__first = _GLIBCXX_MOVE(__val);
2143	    }
2144	  else
2145	    std::__unguarded_linear_insert(__i);
2146	}
2147    }
2148
2149  /// This is a helper function for the sort routine.
2150  template<typename _RandomAccessIterator, typename _Compare>
2151    void
2152    __insertion_sort(_RandomAccessIterator __first,
2153		     _RandomAccessIterator __last, _Compare __comp)
2154    {
2155      if (__first == __last) return;
2156
2157      for (_RandomAccessIterator __i = __first + 1; __i != __last; ++__i)
2158	{
2159	  if (__comp(*__i, *__first))
2160	    {
2161	      typename iterator_traits<_RandomAccessIterator>::value_type
2162		__val = _GLIBCXX_MOVE(*__i);
2163	      _GLIBCXX_MOVE_BACKWARD3(__first, __i, __i + 1);
2164	      *__first = _GLIBCXX_MOVE(__val);
2165	    }
2166	  else
2167	    std::__unguarded_linear_insert(__i, __comp);
2168	}
2169    }
2170
2171  /// This is a helper function for the sort routine.
2172  template<typename _RandomAccessIterator>
2173    inline void
2174    __unguarded_insertion_sort(_RandomAccessIterator __first,
2175			       _RandomAccessIterator __last)
2176    {
2177      typedef typename iterator_traits<_RandomAccessIterator>::value_type
2178	_ValueType;
2179
2180      for (_RandomAccessIterator __i = __first; __i != __last; ++__i)
2181	std::__unguarded_linear_insert(__i);
2182    }
2183
2184  /// This is a helper function for the sort routine.
2185  template<typename _RandomAccessIterator, typename _Compare>
2186    inline void
2187    __unguarded_insertion_sort(_RandomAccessIterator __first,
2188			       _RandomAccessIterator __last, _Compare __comp)
2189    {
2190      typedef typename iterator_traits<_RandomAccessIterator>::value_type
2191	_ValueType;
2192
2193      for (_RandomAccessIterator __i = __first; __i != __last; ++__i)
2194	std::__unguarded_linear_insert(__i, __comp);
2195    }
2196
2197  /**
2198   *  @doctodo
2199   *  This controls some aspect of the sort routines.
2200  */
2201  enum { _S_threshold = 16 };
2202
2203  /// This is a helper function for the sort routine.
2204  template<typename _RandomAccessIterator>
2205    void
2206    __final_insertion_sort(_RandomAccessIterator __first,
2207			   _RandomAccessIterator __last)
2208    {
2209      if (__last - __first > int(_S_threshold))
2210	{
2211	  std::__insertion_sort(__first, __first + int(_S_threshold));
2212	  std::__unguarded_insertion_sort(__first + int(_S_threshold), __last);
2213	}
2214      else
2215	std::__insertion_sort(__first, __last);
2216    }
2217
2218  /// This is a helper function for the sort routine.
2219  template<typename _RandomAccessIterator, typename _Compare>
2220    void
2221    __final_insertion_sort(_RandomAccessIterator __first,
2222			   _RandomAccessIterator __last, _Compare __comp)
2223    {
2224      if (__last - __first > int(_S_threshold))
2225	{
2226	  std::__insertion_sort(__first, __first + int(_S_threshold), __comp);
2227	  std::__unguarded_insertion_sort(__first + int(_S_threshold), __last,
2228					  __comp);
2229	}
2230      else
2231	std::__insertion_sort(__first, __last, __comp);
2232    }
2233
2234  /// This is a helper function...
2235  template<typename _RandomAccessIterator, typename _Tp>
2236    _RandomAccessIterator
2237    __unguarded_partition(_RandomAccessIterator __first,
2238			  _RandomAccessIterator __last, const _Tp& __pivot)
2239    {
2240      while (true)
2241	{
2242	  while (*__first < __pivot)
2243	    ++__first;
2244	  --__last;
2245	  while (__pivot < *__last)
2246	    --__last;
2247	  if (!(__first < __last))
2248	    return __first;
2249	  std::iter_swap(__first, __last);
2250	  ++__first;
2251	}
2252    }
2253
2254  /// This is a helper function...
2255  template<typename _RandomAccessIterator, typename _Tp, typename _Compare>
2256    _RandomAccessIterator
2257    __unguarded_partition(_RandomAccessIterator __first,
2258			  _RandomAccessIterator __last,
2259			  const _Tp& __pivot, _Compare __comp)
2260    {
2261      while (true)
2262	{
2263	  while (__comp(*__first, __pivot))
2264	    ++__first;
2265	  --__last;
2266	  while (__comp(__pivot, *__last))
2267	    --__last;
2268	  if (!(__first < __last))
2269	    return __first;
2270	  std::iter_swap(__first, __last);
2271	  ++__first;
2272	}
2273    }
2274
2275  /// This is a helper function...
2276  template<typename _RandomAccessIterator>
2277    inline _RandomAccessIterator
2278    __unguarded_partition_pivot(_RandomAccessIterator __first,
2279				_RandomAccessIterator __last)
2280    {
2281      _RandomAccessIterator __mid = __first + (__last - __first) / 2;
2282      std::__move_median_to_first(__first, __first + 1, __mid, __last - 1);
2283      return std::__unguarded_partition(__first + 1, __last, *__first);
2284    }
2285
2286
2287  /// This is a helper function...
2288  template<typename _RandomAccessIterator, typename _Compare>
2289    inline _RandomAccessIterator
2290    __unguarded_partition_pivot(_RandomAccessIterator __first,
2291				_RandomAccessIterator __last, _Compare __comp)
2292    {
2293      _RandomAccessIterator __mid = __first + (__last - __first) / 2;
2294      std::__move_median_to_first(__first, __first + 1, __mid, __last - 1,
2295				  __comp);
2296      return std::__unguarded_partition(__first + 1, __last, *__first, __comp);
2297    }
2298
2299  /// This is a helper function for the sort routine.
2300  template<typename _RandomAccessIterator, typename _Size>
2301    void
2302    __introsort_loop(_RandomAccessIterator __first,
2303		     _RandomAccessIterator __last,
2304		     _Size __depth_limit)
2305    {
2306      while (__last - __first > int(_S_threshold))
2307	{
2308	  if (__depth_limit == 0)
2309	    {
2310	      _GLIBCXX_STD_A::partial_sort(__first, __last, __last);
2311	      return;
2312	    }
2313	  --__depth_limit;
2314	  _RandomAccessIterator __cut =
2315	    std::__unguarded_partition_pivot(__first, __last);
2316	  std::__introsort_loop(__cut, __last, __depth_limit);
2317	  __last = __cut;
2318	}
2319    }
2320
2321  /// This is a helper function for the sort routine.
2322  template<typename _RandomAccessIterator, typename _Size, typename _Compare>
2323    void
2324    __introsort_loop(_RandomAccessIterator __first,
2325		     _RandomAccessIterator __last,
2326		     _Size __depth_limit, _Compare __comp)
2327    {
2328      while (__last - __first > int(_S_threshold))
2329	{
2330	  if (__depth_limit == 0)
2331	    {
2332	      _GLIBCXX_STD_A::partial_sort(__first, __last, __last, __comp);
2333	      return;
2334	    }
2335	  --__depth_limit;
2336	  _RandomAccessIterator __cut =
2337	    std::__unguarded_partition_pivot(__first, __last, __comp);
2338	  std::__introsort_loop(__cut, __last, __depth_limit, __comp);
2339	  __last = __cut;
2340	}
2341    }
2342
2343  // sort
2344
2345  template<typename _RandomAccessIterator, typename _Size>
2346    void
2347    __introselect(_RandomAccessIterator __first, _RandomAccessIterator __nth,
2348		  _RandomAccessIterator __last, _Size __depth_limit)
2349    {
2350      typedef typename iterator_traits<_RandomAccessIterator>::value_type
2351	_ValueType;
2352
2353      while (__last - __first > 3)
2354	{
2355	  if (__depth_limit == 0)
2356	    {
2357	      std::__heap_select(__first, __nth + 1, __last);
2358
2359	      // Place the nth largest element in its final position.
2360	      std::iter_swap(__first, __nth);
2361	      return;
2362	    }
2363	  --__depth_limit;
2364	  _RandomAccessIterator __cut =
2365	    std::__unguarded_partition_pivot(__first, __last);
2366	  if (__cut <= __nth)
2367	    __first = __cut;
2368	  else
2369	    __last = __cut;
2370	}
2371      std::__insertion_sort(__first, __last);
2372    }
2373
2374  template<typename _RandomAccessIterator, typename _Size, typename _Compare>
2375    void
2376    __introselect(_RandomAccessIterator __first, _RandomAccessIterator __nth,
2377		  _RandomAccessIterator __last, _Size __depth_limit,
2378		  _Compare __comp)
2379    {
2380      typedef typename iterator_traits<_RandomAccessIterator>::value_type
2381	_ValueType;
2382
2383      while (__last - __first > 3)
2384	{
2385	  if (__depth_limit == 0)
2386	    {
2387	      std::__heap_select(__first, __nth + 1, __last, __comp);
2388	      // Place the nth largest element in its final position.
2389	      std::iter_swap(__first, __nth);
2390	      return;
2391	    }
2392	  --__depth_limit;
2393	  _RandomAccessIterator __cut =
2394	    std::__unguarded_partition_pivot(__first, __last, __comp);
2395	  if (__cut <= __nth)
2396	    __first = __cut;
2397	  else
2398	    __last = __cut;
2399	}
2400      std::__insertion_sort(__first, __last, __comp);
2401    }
2402
2403  // nth_element
2404
2405  // lower_bound moved to stl_algobase.h
2406
2407  /**
2408   *  @brief Finds the first position in which @p __val could be inserted
2409   *         without changing the ordering.
2410   *  @ingroup binary_search_algorithms
2411   *  @param  __first   An iterator.
2412   *  @param  __last    Another iterator.
2413   *  @param  __val     The search term.
2414   *  @param  __comp    A functor to use for comparisons.
2415   *  @return An iterator pointing to the first element <em>not less
2416   *           than</em> @p __val, or end() if every element is less
2417   *           than @p __val.
2418   *  @ingroup binary_search_algorithms
2419   *
2420   *  The comparison function should have the same effects on ordering as
2421   *  the function used for the initial sort.
2422  */
2423  template<typename _ForwardIterator, typename _Tp, typename _Compare>
2424    _ForwardIterator
2425    lower_bound(_ForwardIterator __first, _ForwardIterator __last,
2426		const _Tp& __val, _Compare __comp)
2427    {
2428      typedef typename iterator_traits<_ForwardIterator>::value_type
2429	_ValueType;
2430      typedef typename iterator_traits<_ForwardIterator>::difference_type
2431	_DistanceType;
2432
2433      // concept requirements
2434      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
2435      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
2436				  _ValueType, _Tp>)
2437      __glibcxx_requires_partitioned_lower_pred(__first, __last,
2438						__val, __comp);
2439
2440      _DistanceType __len = std::distance(__first, __last);
2441
2442      while (__len > 0)
2443	{
2444	  _DistanceType __half = __len >> 1;
2445	  _ForwardIterator __middle = __first;
2446	  std::advance(__middle, __half);
2447	  if (__comp(*__middle, __val))
2448	    {
2449	      __first = __middle;
2450	      ++__first;
2451	      __len = __len - __half - 1;
2452	    }
2453	  else
2454	    __len = __half;
2455	}
2456      return __first;
2457    }
2458
2459  /**
2460   *  @brief Finds the last position in which @p __val could be inserted
2461   *         without changing the ordering.
2462   *  @ingroup binary_search_algorithms
2463   *  @param  __first   An iterator.
2464   *  @param  __last    Another iterator.
2465   *  @param  __val     The search term.
2466   *  @return  An iterator pointing to the first element greater than @p __val,
2467   *           or end() if no elements are greater than @p __val.
2468   *  @ingroup binary_search_algorithms
2469  */
2470  template<typename _ForwardIterator, typename _Tp>
2471    _ForwardIterator
2472    upper_bound(_ForwardIterator __first, _ForwardIterator __last,
2473		const _Tp& __val)
2474    {
2475      typedef typename iterator_traits<_ForwardIterator>::value_type
2476	_ValueType;
2477      typedef typename iterator_traits<_ForwardIterator>::difference_type
2478	_DistanceType;
2479
2480      // concept requirements
2481      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
2482      __glibcxx_function_requires(_LessThanOpConcept<_Tp, _ValueType>)
2483      __glibcxx_requires_partitioned_upper(__first, __last, __val);
2484
2485      _DistanceType __len = std::distance(__first, __last);
2486
2487      while (__len > 0)
2488	{
2489	  _DistanceType __half = __len >> 1;
2490	  _ForwardIterator __middle = __first;
2491	  std::advance(__middle, __half);
2492	  if (__val < *__middle)
2493	    __len = __half;
2494	  else
2495	    {
2496	      __first = __middle;
2497	      ++__first;
2498	      __len = __len - __half - 1;
2499	    }
2500	}
2501      return __first;
2502    }
2503
2504  /**
2505   *  @brief Finds the last position in which @p __val could be inserted
2506   *         without changing the ordering.
2507   *  @ingroup binary_search_algorithms
2508   *  @param  __first   An iterator.
2509   *  @param  __last    Another iterator.
2510   *  @param  __val     The search term.
2511   *  @param  __comp    A functor to use for comparisons.
2512   *  @return  An iterator pointing to the first element greater than @p __val,
2513   *           or end() if no elements are greater than @p __val.
2514   *  @ingroup binary_search_algorithms
2515   *
2516   *  The comparison function should have the same effects on ordering as
2517   *  the function used for the initial sort.
2518  */
2519  template<typename _ForwardIterator, typename _Tp, typename _Compare>
2520    _ForwardIterator
2521    upper_bound(_ForwardIterator __first, _ForwardIterator __last,
2522		const _Tp& __val, _Compare __comp)
2523    {
2524      typedef typename iterator_traits<_ForwardIterator>::value_type
2525	_ValueType;
2526      typedef typename iterator_traits<_ForwardIterator>::difference_type
2527	_DistanceType;
2528
2529      // concept requirements
2530      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
2531      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
2532				  _Tp, _ValueType>)
2533      __glibcxx_requires_partitioned_upper_pred(__first, __last,
2534						__val, __comp);
2535
2536      _DistanceType __len = std::distance(__first, __last);
2537
2538      while (__len > 0)
2539	{
2540	  _DistanceType __half = __len >> 1;
2541	  _ForwardIterator __middle = __first;
2542	  std::advance(__middle, __half);
2543	  if (__comp(__val, *__middle))
2544	    __len = __half;
2545	  else
2546	    {
2547	      __first = __middle;
2548	      ++__first;
2549	      __len = __len - __half - 1;
2550	    }
2551	}
2552      return __first;
2553    }
2554
2555  /**
2556   *  @brief Finds the largest subrange in which @p __val could be inserted
2557   *         at any place in it without changing the ordering.
2558   *  @ingroup binary_search_algorithms
2559   *  @param  __first   An iterator.
2560   *  @param  __last    Another iterator.
2561   *  @param  __val     The search term.
2562   *  @return  An pair of iterators defining the subrange.
2563   *  @ingroup binary_search_algorithms
2564   *
2565   *  This is equivalent to
2566   *  @code
2567   *    std::make_pair(lower_bound(__first, __last, __val),
2568   *                   upper_bound(__first, __last, __val))
2569   *  @endcode
2570   *  but does not actually call those functions.
2571  */
2572  template<typename _ForwardIterator, typename _Tp>
2573    pair<_ForwardIterator, _ForwardIterator>
2574    equal_range(_ForwardIterator __first, _ForwardIterator __last,
2575		const _Tp& __val)
2576    {
2577      typedef typename iterator_traits<_ForwardIterator>::value_type
2578	_ValueType;
2579      typedef typename iterator_traits<_ForwardIterator>::difference_type
2580	_DistanceType;
2581
2582      // concept requirements
2583      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
2584      __glibcxx_function_requires(_LessThanOpConcept<_ValueType, _Tp>)
2585      __glibcxx_function_requires(_LessThanOpConcept<_Tp, _ValueType>)
2586      __glibcxx_requires_partitioned_lower(__first, __last, __val);
2587      __glibcxx_requires_partitioned_upper(__first, __last, __val);
2588
2589      _DistanceType __len = std::distance(__first, __last);
2590
2591      while (__len > 0)
2592	{
2593	  _DistanceType __half = __len >> 1;
2594	  _ForwardIterator __middle = __first;
2595	  std::advance(__middle, __half);
2596	  if (*__middle < __val)
2597	    {
2598	      __first = __middle;
2599	      ++__first;
2600	      __len = __len - __half - 1;
2601	    }
2602	  else if (__val < *__middle)
2603	    __len = __half;
2604	  else
2605	    {
2606	      _ForwardIterator __left = std::lower_bound(__first, __middle,
2607							 __val);
2608	      std::advance(__first, __len);
2609	      _ForwardIterator __right = std::upper_bound(++__middle, __first,
2610							  __val);
2611	      return pair<_ForwardIterator, _ForwardIterator>(__left, __right);
2612	    }
2613	}
2614      return pair<_ForwardIterator, _ForwardIterator>(__first, __first);
2615    }
2616
2617  /**
2618   *  @brief Finds the largest subrange in which @p __val could be inserted
2619   *         at any place in it without changing the ordering.
2620   *  @param  __first   An iterator.
2621   *  @param  __last    Another iterator.
2622   *  @param  __val     The search term.
2623   *  @param  __comp    A functor to use for comparisons.
2624   *  @return  An pair of iterators defining the subrange.
2625   *  @ingroup binary_search_algorithms
2626   *
2627   *  This is equivalent to
2628   *  @code
2629   *    std::make_pair(lower_bound(__first, __last, __val, __comp),
2630   *                   upper_bound(__first, __last, __val, __comp))
2631   *  @endcode
2632   *  but does not actually call those functions.
2633  */
2634  template<typename _ForwardIterator, typename _Tp, typename _Compare>
2635    pair<_ForwardIterator, _ForwardIterator>
2636    equal_range(_ForwardIterator __first, _ForwardIterator __last,
2637		const _Tp& __val, _Compare __comp)
2638    {
2639      typedef typename iterator_traits<_ForwardIterator>::value_type
2640	_ValueType;
2641      typedef typename iterator_traits<_ForwardIterator>::difference_type
2642	_DistanceType;
2643
2644      // concept requirements
2645      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
2646      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
2647				  _ValueType, _Tp>)
2648      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
2649				  _Tp, _ValueType>)
2650      __glibcxx_requires_partitioned_lower_pred(__first, __last,
2651						__val, __comp);
2652      __glibcxx_requires_partitioned_upper_pred(__first, __last,
2653						__val, __comp);
2654
2655      _DistanceType __len = std::distance(__first, __last);
2656
2657      while (__len > 0)
2658	{
2659	  _DistanceType __half = __len >> 1;
2660	  _ForwardIterator __middle = __first;
2661	  std::advance(__middle, __half);
2662	  if (__comp(*__middle, __val))
2663	    {
2664	      __first = __middle;
2665	      ++__first;
2666	      __len = __len - __half - 1;
2667	    }
2668	  else if (__comp(__val, *__middle))
2669	    __len = __half;
2670	  else
2671	    {
2672	      _ForwardIterator __left = std::lower_bound(__first, __middle,
2673							 __val, __comp);
2674	      std::advance(__first, __len);
2675	      _ForwardIterator __right = std::upper_bound(++__middle, __first,
2676							  __val, __comp);
2677	      return pair<_ForwardIterator, _ForwardIterator>(__left, __right);
2678	    }
2679	}
2680      return pair<_ForwardIterator, _ForwardIterator>(__first, __first);
2681    }
2682
2683  /**
2684   *  @brief Determines whether an element exists in a range.
2685   *  @ingroup binary_search_algorithms
2686   *  @param  __first   An iterator.
2687   *  @param  __last    Another iterator.
2688   *  @param  __val     The search term.
2689   *  @return True if @p __val (or its equivalent) is in [@p
2690   *  __first,@p __last ].
2691   *
2692   *  Note that this does not actually return an iterator to @p __val.  For
2693   *  that, use std::find or a container's specialized find member functions.
2694  */
2695  template<typename _ForwardIterator, typename _Tp>
2696    bool
2697    binary_search(_ForwardIterator __first, _ForwardIterator __last,
2698                  const _Tp& __val)
2699    {
2700      typedef typename iterator_traits<_ForwardIterator>::value_type
2701	_ValueType;
2702
2703      // concept requirements
2704      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
2705      __glibcxx_function_requires(_LessThanOpConcept<_Tp, _ValueType>)
2706      __glibcxx_requires_partitioned_lower(__first, __last, __val);
2707      __glibcxx_requires_partitioned_upper(__first, __last, __val);
2708
2709      _ForwardIterator __i = std::lower_bound(__first, __last, __val);
2710      return __i != __last && !(__val < *__i);
2711    }
2712
2713  /**
2714   *  @brief Determines whether an element exists in a range.
2715   *  @ingroup binary_search_algorithms
2716   *  @param  __first   An iterator.
2717   *  @param  __last    Another iterator.
2718   *  @param  __val     The search term.
2719   *  @param  __comp    A functor to use for comparisons.
2720   *  @return  True if @p __val (or its equivalent) is in @p [__first,__last].
2721   *
2722   *  Note that this does not actually return an iterator to @p __val.  For
2723   *  that, use std::find or a container's specialized find member functions.
2724   *
2725   *  The comparison function should have the same effects on ordering as
2726   *  the function used for the initial sort.
2727  */
2728  template<typename _ForwardIterator, typename _Tp, typename _Compare>
2729    bool
2730    binary_search(_ForwardIterator __first, _ForwardIterator __last,
2731                  const _Tp& __val, _Compare __comp)
2732    {
2733      typedef typename iterator_traits<_ForwardIterator>::value_type
2734	_ValueType;
2735
2736      // concept requirements
2737      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
2738      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
2739				  _Tp, _ValueType>)
2740      __glibcxx_requires_partitioned_lower_pred(__first, __last,
2741						__val, __comp);
2742      __glibcxx_requires_partitioned_upper_pred(__first, __last,
2743						__val, __comp);
2744
2745      _ForwardIterator __i = std::lower_bound(__first, __last, __val, __comp);
2746      return __i != __last && !bool(__comp(__val, *__i));
2747    }
2748
2749  // merge
2750
2751  /// This is a helper function for the __merge_adaptive routines.
2752  template<typename _InputIterator1, typename _InputIterator2,
2753	   typename _OutputIterator>
2754    void
2755    __move_merge_adaptive(_InputIterator1 __first1, _InputIterator1 __last1,
2756			  _InputIterator2 __first2, _InputIterator2 __last2,
2757			  _OutputIterator __result)
2758    {
2759      while (__first1 != __last1 && __first2 != __last2)
2760	{
2761	  if (*__first2 < *__first1)
2762	    {
2763	      *__result = _GLIBCXX_MOVE(*__first2);
2764	      ++__first2;
2765	    }
2766	  else
2767	    {
2768	      *__result = _GLIBCXX_MOVE(*__first1);
2769	      ++__first1;
2770	    }
2771	  ++__result;
2772	}
2773      if (__first1 != __last1)
2774	_GLIBCXX_MOVE3(__first1, __last1, __result);
2775    }
2776
2777  /// This is a helper function for the __merge_adaptive routines.
2778  template<typename _InputIterator1, typename _InputIterator2,
2779	   typename _OutputIterator, typename _Compare>
2780    void
2781    __move_merge_adaptive(_InputIterator1 __first1, _InputIterator1 __last1,
2782			  _InputIterator2 __first2, _InputIterator2 __last2,
2783			  _OutputIterator __result, _Compare __comp)
2784    {
2785      while (__first1 != __last1 && __first2 != __last2)
2786	{
2787	  if (__comp(*__first2, *__first1))
2788	    {
2789	      *__result = _GLIBCXX_MOVE(*__first2);
2790	      ++__first2;
2791	    }
2792	  else
2793	    {
2794	      *__result = _GLIBCXX_MOVE(*__first1);
2795	      ++__first1;
2796	    }
2797	  ++__result;
2798	}
2799      if (__first1 != __last1)
2800	_GLIBCXX_MOVE3(__first1, __last1, __result);
2801    }
2802
2803  /// This is a helper function for the __merge_adaptive routines.
2804  template<typename _BidirectionalIterator1, typename _BidirectionalIterator2,
2805	   typename _BidirectionalIterator3>
2806    void
2807    __move_merge_adaptive_backward(_BidirectionalIterator1 __first1,
2808				   _BidirectionalIterator1 __last1,
2809				   _BidirectionalIterator2 __first2,
2810				   _BidirectionalIterator2 __last2,
2811				   _BidirectionalIterator3 __result)
2812    {
2813      if (__first1 == __last1)
2814	{
2815	  _GLIBCXX_MOVE_BACKWARD3(__first2, __last2, __result);
2816	  return;
2817	}
2818      else if (__first2 == __last2)
2819	return;
2820
2821      --__last1;
2822      --__last2;
2823      while (true)
2824	{
2825	  if (*__last2 < *__last1)
2826	    {
2827	      *--__result = _GLIBCXX_MOVE(*__last1);
2828	      if (__first1 == __last1)
2829		{
2830		  _GLIBCXX_MOVE_BACKWARD3(__first2, ++__last2, __result);
2831		  return;
2832		}
2833	      --__last1;
2834	    }
2835	  else
2836	    {
2837	      *--__result = _GLIBCXX_MOVE(*__last2);
2838	      if (__first2 == __last2)
2839		return;
2840	      --__last2;
2841	    }
2842	}
2843    }
2844
2845  /// This is a helper function for the __merge_adaptive routines.
2846  template<typename _BidirectionalIterator1, typename _BidirectionalIterator2,
2847	   typename _BidirectionalIterator3, typename _Compare>
2848    void
2849    __move_merge_adaptive_backward(_BidirectionalIterator1 __first1,
2850				   _BidirectionalIterator1 __last1,
2851				   _BidirectionalIterator2 __first2,
2852				   _BidirectionalIterator2 __last2,
2853				   _BidirectionalIterator3 __result,
2854				   _Compare __comp)
2855    {
2856      if (__first1 == __last1)
2857	{
2858	  _GLIBCXX_MOVE_BACKWARD3(__first2, __last2, __result);
2859	  return;
2860	}
2861      else if (__first2 == __last2)
2862	return;
2863
2864      --__last1;
2865      --__last2;
2866      while (true)
2867	{
2868	  if (__comp(*__last2, *__last1))
2869	    {
2870	      *--__result = _GLIBCXX_MOVE(*__last1);
2871	      if (__first1 == __last1)
2872		{
2873		  _GLIBCXX_MOVE_BACKWARD3(__first2, ++__last2, __result);
2874		  return;
2875		}
2876	      --__last1;
2877	    }
2878	  else
2879	    {
2880	      *--__result = _GLIBCXX_MOVE(*__last2);
2881	      if (__first2 == __last2)
2882		return;
2883	      --__last2;
2884	    }
2885	}
2886    }
2887
2888  /// This is a helper function for the merge routines.
2889  template<typename _BidirectionalIterator1, typename _BidirectionalIterator2,
2890	   typename _Distance>
2891    _BidirectionalIterator1
2892    __rotate_adaptive(_BidirectionalIterator1 __first,
2893		      _BidirectionalIterator1 __middle,
2894		      _BidirectionalIterator1 __last,
2895		      _Distance __len1, _Distance __len2,
2896		      _BidirectionalIterator2 __buffer,
2897		      _Distance __buffer_size)
2898    {
2899      _BidirectionalIterator2 __buffer_end;
2900      if (__len1 > __len2 && __len2 <= __buffer_size)
2901	{
2902	  if (__len2)
2903	    {
2904	      __buffer_end = _GLIBCXX_MOVE3(__middle, __last, __buffer);
2905	      _GLIBCXX_MOVE_BACKWARD3(__first, __middle, __last);
2906	      return _GLIBCXX_MOVE3(__buffer, __buffer_end, __first);
2907	    }
2908	  else
2909	    return __first;
2910	}
2911      else if (__len1 <= __buffer_size)
2912	{
2913	  if (__len1)
2914	    {
2915	      __buffer_end = _GLIBCXX_MOVE3(__first, __middle, __buffer);
2916	      _GLIBCXX_MOVE3(__middle, __last, __first);
2917	      return _GLIBCXX_MOVE_BACKWARD3(__buffer, __buffer_end, __last);
2918	    }
2919	  else
2920	    return __last;
2921	}
2922      else
2923	{
2924	  std::rotate(__first, __middle, __last);
2925	  std::advance(__first, std::distance(__middle, __last));
2926	  return __first;
2927	}
2928    }
2929
2930  /// This is a helper function for the merge routines.
2931  template<typename _BidirectionalIterator, typename _Distance,
2932	   typename _Pointer>
2933    void
2934    __merge_adaptive(_BidirectionalIterator __first,
2935                     _BidirectionalIterator __middle,
2936		     _BidirectionalIterator __last,
2937		     _Distance __len1, _Distance __len2,
2938		     _Pointer __buffer, _Distance __buffer_size)
2939    {
2940      if (__len1 <= __len2 && __len1 <= __buffer_size)
2941	{
2942	  _Pointer __buffer_end = _GLIBCXX_MOVE3(__first, __middle, __buffer);
2943	  std::__move_merge_adaptive(__buffer, __buffer_end, __middle, __last,
2944				     __first);
2945	}
2946      else if (__len2 <= __buffer_size)
2947	{
2948	  _Pointer __buffer_end = _GLIBCXX_MOVE3(__middle, __last, __buffer);
2949	  std::__move_merge_adaptive_backward(__first, __middle, __buffer,
2950					      __buffer_end, __last);
2951	}
2952      else
2953	{
2954	  _BidirectionalIterator __first_cut = __first;
2955	  _BidirectionalIterator __second_cut = __middle;
2956	  _Distance __len11 = 0;
2957	  _Distance __len22 = 0;
2958	  if (__len1 > __len2)
2959	    {
2960	      __len11 = __len1 / 2;
2961	      std::advance(__first_cut, __len11);
2962	      __second_cut = std::lower_bound(__middle, __last,
2963					      *__first_cut);
2964	      __len22 = std::distance(__middle, __second_cut);
2965	    }
2966	  else
2967	    {
2968	      __len22 = __len2 / 2;
2969	      std::advance(__second_cut, __len22);
2970	      __first_cut = std::upper_bound(__first, __middle,
2971					     *__second_cut);
2972	      __len11 = std::distance(__first, __first_cut);
2973	    }
2974	  _BidirectionalIterator __new_middle =
2975	    std::__rotate_adaptive(__first_cut, __middle, __second_cut,
2976				   __len1 - __len11, __len22, __buffer,
2977				   __buffer_size);
2978	  std::__merge_adaptive(__first, __first_cut, __new_middle, __len11,
2979				__len22, __buffer, __buffer_size);
2980	  std::__merge_adaptive(__new_middle, __second_cut, __last,
2981				__len1 - __len11,
2982				__len2 - __len22, __buffer, __buffer_size);
2983	}
2984    }
2985
2986  /// This is a helper function for the merge routines.
2987  template<typename _BidirectionalIterator, typename _Distance,
2988	   typename _Pointer, typename _Compare>
2989    void
2990    __merge_adaptive(_BidirectionalIterator __first,
2991                     _BidirectionalIterator __middle,
2992		     _BidirectionalIterator __last,
2993		     _Distance __len1, _Distance __len2,
2994		     _Pointer __buffer, _Distance __buffer_size,
2995		     _Compare __comp)
2996    {
2997      if (__len1 <= __len2 && __len1 <= __buffer_size)
2998	{
2999	  _Pointer __buffer_end = _GLIBCXX_MOVE3(__first, __middle, __buffer);
3000	  std::__move_merge_adaptive(__buffer, __buffer_end, __middle, __last,
3001				     __first, __comp);
3002	}
3003      else if (__len2 <= __buffer_size)
3004	{
3005	  _Pointer __buffer_end = _GLIBCXX_MOVE3(__middle, __last, __buffer);
3006	  std::__move_merge_adaptive_backward(__first, __middle, __buffer,
3007					      __buffer_end, __last, __comp);
3008	}
3009      else
3010	{
3011	  _BidirectionalIterator __first_cut = __first;
3012	  _BidirectionalIterator __second_cut = __middle;
3013	  _Distance __len11 = 0;
3014	  _Distance __len22 = 0;
3015	  if (__len1 > __len2)
3016	    {
3017	      __len11 = __len1 / 2;
3018	      std::advance(__first_cut, __len11);
3019	      __second_cut = std::lower_bound(__middle, __last, *__first_cut,
3020					      __comp);
3021	      __len22 = std::distance(__middle, __second_cut);
3022	    }
3023	  else
3024	    {
3025	      __len22 = __len2 / 2;
3026	      std::advance(__second_cut, __len22);
3027	      __first_cut = std::upper_bound(__first, __middle, *__second_cut,
3028					     __comp);
3029	      __len11 = std::distance(__first, __first_cut);
3030	    }
3031	  _BidirectionalIterator __new_middle =
3032	    std::__rotate_adaptive(__first_cut, __middle, __second_cut,
3033				   __len1 - __len11, __len22, __buffer,
3034				   __buffer_size);
3035	  std::__merge_adaptive(__first, __first_cut, __new_middle, __len11,
3036				__len22, __buffer, __buffer_size, __comp);
3037	  std::__merge_adaptive(__new_middle, __second_cut, __last,
3038				__len1 - __len11,
3039				__len2 - __len22, __buffer,
3040				__buffer_size, __comp);
3041	}
3042    }
3043
3044  /// This is a helper function for the merge routines.
3045  template<typename _BidirectionalIterator, typename _Distance>
3046    void
3047    __merge_without_buffer(_BidirectionalIterator __first,
3048			   _BidirectionalIterator __middle,
3049			   _BidirectionalIterator __last,
3050			   _Distance __len1, _Distance __len2)
3051    {
3052      if (__len1 == 0 || __len2 == 0)
3053	return;
3054      if (__len1 + __len2 == 2)
3055	{
3056	  if (*__middle < *__first)
3057	    std::iter_swap(__first, __middle);
3058	  return;
3059	}
3060      _BidirectionalIterator __first_cut = __first;
3061      _BidirectionalIterator __second_cut = __middle;
3062      _Distance __len11 = 0;
3063      _Distance __len22 = 0;
3064      if (__len1 > __len2)
3065	{
3066	  __len11 = __len1 / 2;
3067	  std::advance(__first_cut, __len11);
3068	  __second_cut = std::lower_bound(__middle, __last, *__first_cut);
3069	  __len22 = std::distance(__middle, __second_cut);
3070	}
3071      else
3072	{
3073	  __len22 = __len2 / 2;
3074	  std::advance(__second_cut, __len22);
3075	  __first_cut = std::upper_bound(__first, __middle, *__second_cut);
3076	  __len11 = std::distance(__first, __first_cut);
3077	}
3078      std::rotate(__first_cut, __middle, __second_cut);
3079      _BidirectionalIterator __new_middle = __first_cut;
3080      std::advance(__new_middle, std::distance(__middle, __second_cut));
3081      std::__merge_without_buffer(__first, __first_cut, __new_middle,
3082				  __len11, __len22);
3083      std::__merge_without_buffer(__new_middle, __second_cut, __last,
3084				  __len1 - __len11, __len2 - __len22);
3085    }
3086
3087  /// This is a helper function for the merge routines.
3088  template<typename _BidirectionalIterator, typename _Distance,
3089	   typename _Compare>
3090    void
3091    __merge_without_buffer(_BidirectionalIterator __first,
3092                           _BidirectionalIterator __middle,
3093			   _BidirectionalIterator __last,
3094			   _Distance __len1, _Distance __len2,
3095			   _Compare __comp)
3096    {
3097      if (__len1 == 0 || __len2 == 0)
3098	return;
3099      if (__len1 + __len2 == 2)
3100	{
3101	  if (__comp(*__middle, *__first))
3102	    std::iter_swap(__first, __middle);
3103	  return;
3104	}
3105      _BidirectionalIterator __first_cut = __first;
3106      _BidirectionalIterator __second_cut = __middle;
3107      _Distance __len11 = 0;
3108      _Distance __len22 = 0;
3109      if (__len1 > __len2)
3110	{
3111	  __len11 = __len1 / 2;
3112	  std::advance(__first_cut, __len11);
3113	  __second_cut = std::lower_bound(__middle, __last, *__first_cut,
3114					  __comp);
3115	  __len22 = std::distance(__middle, __second_cut);
3116	}
3117      else
3118	{
3119	  __len22 = __len2 / 2;
3120	  std::advance(__second_cut, __len22);
3121	  __first_cut = std::upper_bound(__first, __middle, *__second_cut,
3122					 __comp);
3123	  __len11 = std::distance(__first, __first_cut);
3124	}
3125      std::rotate(__first_cut, __middle, __second_cut);
3126      _BidirectionalIterator __new_middle = __first_cut;
3127      std::advance(__new_middle, std::distance(__middle, __second_cut));
3128      std::__merge_without_buffer(__first, __first_cut, __new_middle,
3129				  __len11, __len22, __comp);
3130      std::__merge_without_buffer(__new_middle, __second_cut, __last,
3131				  __len1 - __len11, __len2 - __len22, __comp);
3132    }
3133
3134  /**
3135   *  @brief Merges two sorted ranges in place.
3136   *  @ingroup sorting_algorithms
3137   *  @param  __first   An iterator.
3138   *  @param  __middle  Another iterator.
3139   *  @param  __last    Another iterator.
3140   *  @return  Nothing.
3141   *
3142   *  Merges two sorted and consecutive ranges, [__first,__middle) and
3143   *  [__middle,__last), and puts the result in [__first,__last).  The
3144   *  output will be sorted.  The sort is @e stable, that is, for
3145   *  equivalent elements in the two ranges, elements from the first
3146   *  range will always come before elements from the second.
3147   *
3148   *  If enough additional memory is available, this takes (__last-__first)-1
3149   *  comparisons.  Otherwise an NlogN algorithm is used, where N is
3150   *  distance(__first,__last).
3151  */
3152  template<typename _BidirectionalIterator>
3153    void
3154    inplace_merge(_BidirectionalIterator __first,
3155		  _BidirectionalIterator __middle,
3156		  _BidirectionalIterator __last)
3157    {
3158      typedef typename iterator_traits<_BidirectionalIterator>::value_type
3159          _ValueType;
3160      typedef typename iterator_traits<_BidirectionalIterator>::difference_type
3161          _DistanceType;
3162
3163      // concept requirements
3164      __glibcxx_function_requires(_Mutable_BidirectionalIteratorConcept<
3165	    _BidirectionalIterator>)
3166      __glibcxx_function_requires(_LessThanComparableConcept<_ValueType>)
3167      __glibcxx_requires_sorted(__first, __middle);
3168      __glibcxx_requires_sorted(__middle, __last);
3169
3170      if (__first == __middle || __middle == __last)
3171	return;
3172
3173      _DistanceType __len1 = std::distance(__first, __middle);
3174      _DistanceType __len2 = std::distance(__middle, __last);
3175
3176      _Temporary_buffer<_BidirectionalIterator, _ValueType> __buf(__first,
3177								  __last);
3178      if (__buf.begin() == 0)
3179	std::__merge_without_buffer(__first, __middle, __last, __len1, __len2);
3180      else
3181	std::__merge_adaptive(__first, __middle, __last, __len1, __len2,
3182			      __buf.begin(), _DistanceType(__buf.size()));
3183    }
3184
3185  /**
3186   *  @brief Merges two sorted ranges in place.
3187   *  @ingroup sorting_algorithms
3188   *  @param  __first   An iterator.
3189   *  @param  __middle  Another iterator.
3190   *  @param  __last    Another iterator.
3191   *  @param  __comp    A functor to use for comparisons.
3192   *  @return  Nothing.
3193   *
3194   *  Merges two sorted and consecutive ranges, [__first,__middle) and
3195   *  [middle,last), and puts the result in [__first,__last).  The output will
3196   *  be sorted.  The sort is @e stable, that is, for equivalent
3197   *  elements in the two ranges, elements from the first range will always
3198   *  come before elements from the second.
3199   *
3200   *  If enough additional memory is available, this takes (__last-__first)-1
3201   *  comparisons.  Otherwise an NlogN algorithm is used, where N is
3202   *  distance(__first,__last).
3203   *
3204   *  The comparison function should have the same effects on ordering as
3205   *  the function used for the initial sort.
3206  */
3207  template<typename _BidirectionalIterator, typename _Compare>
3208    void
3209    inplace_merge(_BidirectionalIterator __first,
3210		  _BidirectionalIterator __middle,
3211		  _BidirectionalIterator __last,
3212		  _Compare __comp)
3213    {
3214      typedef typename iterator_traits<_BidirectionalIterator>::value_type
3215          _ValueType;
3216      typedef typename iterator_traits<_BidirectionalIterator>::difference_type
3217          _DistanceType;
3218
3219      // concept requirements
3220      __glibcxx_function_requires(_Mutable_BidirectionalIteratorConcept<
3221	    _BidirectionalIterator>)
3222      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
3223	    _ValueType, _ValueType>)
3224      __glibcxx_requires_sorted_pred(__first, __middle, __comp);
3225      __glibcxx_requires_sorted_pred(__middle, __last, __comp);
3226
3227      if (__first == __middle || __middle == __last)
3228	return;
3229
3230      const _DistanceType __len1 = std::distance(__first, __middle);
3231      const _DistanceType __len2 = std::distance(__middle, __last);
3232
3233      _Temporary_buffer<_BidirectionalIterator, _ValueType> __buf(__first,
3234								  __last);
3235      if (__buf.begin() == 0)
3236	std::__merge_without_buffer(__first, __middle, __last, __len1,
3237				    __len2, __comp);
3238      else
3239	std::__merge_adaptive(__first, __middle, __last, __len1, __len2,
3240			      __buf.begin(), _DistanceType(__buf.size()),
3241			      __comp);
3242    }
3243
3244
3245  /// This is a helper function for the __merge_sort_loop routines.
3246  template<typename _InputIterator1, typename _InputIterator2,
3247	   typename _OutputIterator>
3248    _OutputIterator
3249    __move_merge(_InputIterator1 __first1, _InputIterator1 __last1,
3250		 _InputIterator2 __first2, _InputIterator2 __last2,
3251		 _OutputIterator __result)
3252    {
3253      while (__first1 != __last1 && __first2 != __last2)
3254	{
3255	  if (*__first2 < *__first1)
3256	    {
3257	      *__result = _GLIBCXX_MOVE(*__first2);
3258	      ++__first2;
3259	    }
3260	  else
3261	    {
3262	      *__result = _GLIBCXX_MOVE(*__first1);
3263	      ++__first1;
3264	    }
3265	  ++__result;
3266	}
3267      return _GLIBCXX_MOVE3(__first2, __last2,
3268			    _GLIBCXX_MOVE3(__first1, __last1,
3269					   __result));
3270    }
3271
3272  /// This is a helper function for the __merge_sort_loop routines.
3273  template<typename _InputIterator1, typename _InputIterator2,
3274	   typename _OutputIterator, typename _Compare>
3275    _OutputIterator
3276    __move_merge(_InputIterator1 __first1, _InputIterator1 __last1,
3277		 _InputIterator2 __first2, _InputIterator2 __last2,
3278		 _OutputIterator __result, _Compare __comp)
3279    {
3280      while (__first1 != __last1 && __first2 != __last2)
3281	{
3282	  if (__comp(*__first2, *__first1))
3283	    {
3284	      *__result = _GLIBCXX_MOVE(*__first2);
3285	      ++__first2;
3286	    }
3287	  else
3288	    {
3289	      *__result = _GLIBCXX_MOVE(*__first1);
3290	      ++__first1;
3291	    }
3292	  ++__result;
3293	}
3294      return _GLIBCXX_MOVE3(__first2, __last2,
3295			    _GLIBCXX_MOVE3(__first1, __last1,
3296					   __result));
3297    }
3298
3299  template<typename _RandomAccessIterator1, typename _RandomAccessIterator2,
3300	   typename _Distance>
3301    void
3302    __merge_sort_loop(_RandomAccessIterator1 __first,
3303		      _RandomAccessIterator1 __last,
3304		      _RandomAccessIterator2 __result,
3305		      _Distance __step_size)
3306    {
3307      const _Distance __two_step = 2 * __step_size;
3308
3309      while (__last - __first >= __two_step)
3310	{
3311	  __result = std::__move_merge(__first, __first + __step_size,
3312				       __first + __step_size,
3313				       __first + __two_step, __result);
3314	  __first += __two_step;
3315	}
3316
3317      __step_size = std::min(_Distance(__last - __first), __step_size);
3318      std::__move_merge(__first, __first + __step_size,
3319			__first + __step_size, __last, __result);
3320    }
3321
3322  template<typename _RandomAccessIterator1, typename _RandomAccessIterator2,
3323	   typename _Distance, typename _Compare>
3324    void
3325    __merge_sort_loop(_RandomAccessIterator1 __first,
3326		      _RandomAccessIterator1 __last,
3327		      _RandomAccessIterator2 __result, _Distance __step_size,
3328		      _Compare __comp)
3329    {
3330      const _Distance __two_step = 2 * __step_size;
3331
3332      while (__last - __first >= __two_step)
3333	{
3334	  __result = std::__move_merge(__first, __first + __step_size,
3335				       __first + __step_size,
3336				       __first + __two_step,
3337				       __result, __comp);
3338	  __first += __two_step;
3339	}
3340      __step_size = std::min(_Distance(__last - __first), __step_size);
3341
3342      std::__move_merge(__first,__first + __step_size,
3343			__first + __step_size, __last, __result, __comp);
3344    }
3345
3346  template<typename _RandomAccessIterator, typename _Distance>
3347    void
3348    __chunk_insertion_sort(_RandomAccessIterator __first,
3349			   _RandomAccessIterator __last,
3350			   _Distance __chunk_size)
3351    {
3352      while (__last - __first >= __chunk_size)
3353	{
3354	  std::__insertion_sort(__first, __first + __chunk_size);
3355	  __first += __chunk_size;
3356	}
3357      std::__insertion_sort(__first, __last);
3358    }
3359
3360  template<typename _RandomAccessIterator, typename _Distance,
3361	   typename _Compare>
3362    void
3363    __chunk_insertion_sort(_RandomAccessIterator __first,
3364			   _RandomAccessIterator __last,
3365			   _Distance __chunk_size, _Compare __comp)
3366    {
3367      while (__last - __first >= __chunk_size)
3368	{
3369	  std::__insertion_sort(__first, __first + __chunk_size, __comp);
3370	  __first += __chunk_size;
3371	}
3372      std::__insertion_sort(__first, __last, __comp);
3373    }
3374
3375  enum { _S_chunk_size = 7 };
3376
3377  template<typename _RandomAccessIterator, typename _Pointer>
3378    void
3379    __merge_sort_with_buffer(_RandomAccessIterator __first,
3380			     _RandomAccessIterator __last,
3381                             _Pointer __buffer)
3382    {
3383      typedef typename iterator_traits<_RandomAccessIterator>::difference_type
3384	_Distance;
3385
3386      const _Distance __len = __last - __first;
3387      const _Pointer __buffer_last = __buffer + __len;
3388
3389      _Distance __step_size = _S_chunk_size;
3390      std::__chunk_insertion_sort(__first, __last, __step_size);
3391
3392      while (__step_size < __len)
3393	{
3394	  std::__merge_sort_loop(__first, __last, __buffer, __step_size);
3395	  __step_size *= 2;
3396	  std::__merge_sort_loop(__buffer, __buffer_last, __first, __step_size);
3397	  __step_size *= 2;
3398	}
3399    }
3400
3401  template<typename _RandomAccessIterator, typename _Pointer, typename _Compare>
3402    void
3403    __merge_sort_with_buffer(_RandomAccessIterator __first,
3404			     _RandomAccessIterator __last,
3405                             _Pointer __buffer, _Compare __comp)
3406    {
3407      typedef typename iterator_traits<_RandomAccessIterator>::difference_type
3408	_Distance;
3409
3410      const _Distance __len = __last - __first;
3411      const _Pointer __buffer_last = __buffer + __len;
3412
3413      _Distance __step_size = _S_chunk_size;
3414      std::__chunk_insertion_sort(__first, __last, __step_size, __comp);
3415
3416      while (__step_size < __len)
3417	{
3418	  std::__merge_sort_loop(__first, __last, __buffer,
3419				 __step_size, __comp);
3420	  __step_size *= 2;
3421	  std::__merge_sort_loop(__buffer, __buffer_last, __first,
3422				 __step_size, __comp);
3423	  __step_size *= 2;
3424	}
3425    }
3426
3427  template<typename _RandomAccessIterator, typename _Pointer,
3428	   typename _Distance>
3429    void
3430    __stable_sort_adaptive(_RandomAccessIterator __first,
3431			   _RandomAccessIterator __last,
3432                           _Pointer __buffer, _Distance __buffer_size)
3433    {
3434      const _Distance __len = (__last - __first + 1) / 2;
3435      const _RandomAccessIterator __middle = __first + __len;
3436      if (__len > __buffer_size)
3437	{
3438	  std::__stable_sort_adaptive(__first, __middle,
3439				      __buffer, __buffer_size);
3440	  std::__stable_sort_adaptive(__middle, __last,
3441				      __buffer, __buffer_size);
3442	}
3443      else
3444	{
3445	  std::__merge_sort_with_buffer(__first, __middle, __buffer);
3446	  std::__merge_sort_with_buffer(__middle, __last, __buffer);
3447	}
3448      std::__merge_adaptive(__first, __middle, __last,
3449			    _Distance(__middle - __first),
3450			    _Distance(__last - __middle),
3451			    __buffer, __buffer_size);
3452    }
3453
3454  template<typename _RandomAccessIterator, typename _Pointer,
3455	   typename _Distance, typename _Compare>
3456    void
3457    __stable_sort_adaptive(_RandomAccessIterator __first,
3458			   _RandomAccessIterator __last,
3459                           _Pointer __buffer, _Distance __buffer_size,
3460                           _Compare __comp)
3461    {
3462      const _Distance __len = (__last - __first + 1) / 2;
3463      const _RandomAccessIterator __middle = __first + __len;
3464      if (__len > __buffer_size)
3465	{
3466	  std::__stable_sort_adaptive(__first, __middle, __buffer,
3467				      __buffer_size, __comp);
3468	  std::__stable_sort_adaptive(__middle, __last, __buffer,
3469				      __buffer_size, __comp);
3470	}
3471      else
3472	{
3473	  std::__merge_sort_with_buffer(__first, __middle, __buffer, __comp);
3474	  std::__merge_sort_with_buffer(__middle, __last, __buffer, __comp);
3475	}
3476      std::__merge_adaptive(__first, __middle, __last,
3477			    _Distance(__middle - __first),
3478			    _Distance(__last - __middle),
3479			    __buffer, __buffer_size,
3480			    __comp);
3481    }
3482
3483  /// This is a helper function for the stable sorting routines.
3484  template<typename _RandomAccessIterator>
3485    void
3486    __inplace_stable_sort(_RandomAccessIterator __first,
3487			  _RandomAccessIterator __last)
3488    {
3489      if (__last - __first < 15)
3490	{
3491	  std::__insertion_sort(__first, __last);
3492	  return;
3493	}
3494      _RandomAccessIterator __middle = __first + (__last - __first) / 2;
3495      std::__inplace_stable_sort(__first, __middle);
3496      std::__inplace_stable_sort(__middle, __last);
3497      std::__merge_without_buffer(__first, __middle, __last,
3498				  __middle - __first,
3499				  __last - __middle);
3500    }
3501
3502  /// This is a helper function for the stable sorting routines.
3503  template<typename _RandomAccessIterator, typename _Compare>
3504    void
3505    __inplace_stable_sort(_RandomAccessIterator __first,
3506			  _RandomAccessIterator __last, _Compare __comp)
3507    {
3508      if (__last - __first < 15)
3509	{
3510	  std::__insertion_sort(__first, __last, __comp);
3511	  return;
3512	}
3513      _RandomAccessIterator __middle = __first + (__last - __first) / 2;
3514      std::__inplace_stable_sort(__first, __middle, __comp);
3515      std::__inplace_stable_sort(__middle, __last, __comp);
3516      std::__merge_without_buffer(__first, __middle, __last,
3517				  __middle - __first,
3518				  __last - __middle,
3519				  __comp);
3520    }
3521
3522  // stable_sort
3523
3524  // Set algorithms: includes, set_union, set_intersection, set_difference,
3525  // set_symmetric_difference.  All of these algorithms have the precondition
3526  // that their input ranges are sorted and the postcondition that their output
3527  // ranges are sorted.
3528
3529  /**
3530   *  @brief Determines whether all elements of a sequence exists in a range.
3531   *  @param  __first1  Start of search range.
3532   *  @param  __last1   End of search range.
3533   *  @param  __first2  Start of sequence
3534   *  @param  __last2   End of sequence.
3535   *  @return  True if each element in [__first2,__last2) is contained in order
3536   *  within [__first1,__last1).  False otherwise.
3537   *  @ingroup set_algorithms
3538   *
3539   *  This operation expects both [__first1,__last1) and
3540   *  [__first2,__last2) to be sorted.  Searches for the presence of
3541   *  each element in [__first2,__last2) within [__first1,__last1).
3542   *  The iterators over each range only move forward, so this is a
3543   *  linear algorithm.  If an element in [__first2,__last2) is not
3544   *  found before the search iterator reaches @p __last2, false is
3545   *  returned.
3546  */
3547  template<typename _InputIterator1, typename _InputIterator2>
3548    bool
3549    includes(_InputIterator1 __first1, _InputIterator1 __last1,
3550	     _InputIterator2 __first2, _InputIterator2 __last2)
3551    {
3552      typedef typename iterator_traits<_InputIterator1>::value_type
3553	_ValueType1;
3554      typedef typename iterator_traits<_InputIterator2>::value_type
3555	_ValueType2;
3556
3557      // concept requirements
3558      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
3559      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
3560      __glibcxx_function_requires(_LessThanOpConcept<_ValueType1, _ValueType2>)
3561      __glibcxx_function_requires(_LessThanOpConcept<_ValueType2, _ValueType1>)
3562      __glibcxx_requires_sorted_set(__first1, __last1, __first2);
3563      __glibcxx_requires_sorted_set(__first2, __last2, __first1);
3564
3565      while (__first1 != __last1 && __first2 != __last2)
3566	if (*__first2 < *__first1)
3567	  return false;
3568	else if(*__first1 < *__first2)
3569	  ++__first1;
3570	else
3571	  ++__first1, ++__first2;
3572
3573      return __first2 == __last2;
3574    }
3575
3576  /**
3577   *  @brief Determines whether all elements of a sequence exists in a range
3578   *  using comparison.
3579   *  @ingroup set_algorithms
3580   *  @param  __first1  Start of search range.
3581   *  @param  __last1   End of search range.
3582   *  @param  __first2  Start of sequence
3583   *  @param  __last2   End of sequence.
3584   *  @param  __comp    Comparison function to use.
3585   *  @return True if each element in [__first2,__last2) is contained
3586   *  in order within [__first1,__last1) according to comp.  False
3587   *  otherwise.  @ingroup set_algorithms
3588   *
3589   *  This operation expects both [__first1,__last1) and
3590   *  [__first2,__last2) to be sorted.  Searches for the presence of
3591   *  each element in [__first2,__last2) within [__first1,__last1),
3592   *  using comp to decide.  The iterators over each range only move
3593   *  forward, so this is a linear algorithm.  If an element in
3594   *  [__first2,__last2) is not found before the search iterator
3595   *  reaches @p __last2, false is returned.
3596  */
3597  template<typename _InputIterator1, typename _InputIterator2,
3598	   typename _Compare>
3599    bool
3600    includes(_InputIterator1 __first1, _InputIterator1 __last1,
3601	     _InputIterator2 __first2, _InputIterator2 __last2,
3602	     _Compare __comp)
3603    {
3604      typedef typename iterator_traits<_InputIterator1>::value_type
3605	_ValueType1;
3606      typedef typename iterator_traits<_InputIterator2>::value_type
3607	_ValueType2;
3608
3609      // concept requirements
3610      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
3611      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
3612      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
3613				  _ValueType1, _ValueType2>)
3614      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
3615				  _ValueType2, _ValueType1>)
3616      __glibcxx_requires_sorted_set_pred(__first1, __last1, __first2, __comp);
3617      __glibcxx_requires_sorted_set_pred(__first2, __last2, __first1, __comp);
3618
3619      while (__first1 != __last1 && __first2 != __last2)
3620	if (__comp(*__first2, *__first1))
3621	  return false;
3622	else if(__comp(*__first1, *__first2))
3623	  ++__first1;
3624	else
3625	  ++__first1, ++__first2;
3626
3627      return __first2 == __last2;
3628    }
3629
3630  // nth_element
3631  // merge
3632  // set_difference
3633  // set_intersection
3634  // set_union
3635  // stable_sort
3636  // set_symmetric_difference
3637  // min_element
3638  // max_element
3639
3640  /**
3641   *  @brief  Permute range into the next @e dictionary ordering.
3642   *  @ingroup sorting_algorithms
3643   *  @param  __first  Start of range.
3644   *  @param  __last   End of range.
3645   *  @return  False if wrapped to first permutation, true otherwise.
3646   *
3647   *  Treats all permutations of the range as a set of @e dictionary sorted
3648   *  sequences.  Permutes the current sequence into the next one of this set.
3649   *  Returns true if there are more sequences to generate.  If the sequence
3650   *  is the largest of the set, the smallest is generated and false returned.
3651  */
3652  template<typename _BidirectionalIterator>
3653    bool
3654    next_permutation(_BidirectionalIterator __first,
3655		     _BidirectionalIterator __last)
3656    {
3657      // concept requirements
3658      __glibcxx_function_requires(_BidirectionalIteratorConcept<
3659				  _BidirectionalIterator>)
3660      __glibcxx_function_requires(_LessThanComparableConcept<
3661	    typename iterator_traits<_BidirectionalIterator>::value_type>)
3662      __glibcxx_requires_valid_range(__first, __last);
3663
3664      if (__first == __last)
3665	return false;
3666      _BidirectionalIterator __i = __first;
3667      ++__i;
3668      if (__i == __last)
3669	return false;
3670      __i = __last;
3671      --__i;
3672
3673      for(;;)
3674	{
3675	  _BidirectionalIterator __ii = __i;
3676	  --__i;
3677	  if (*__i < *__ii)
3678	    {
3679	      _BidirectionalIterator __j = __last;
3680	      while (!(*__i < *--__j))
3681		{}
3682	      std::iter_swap(__i, __j);
3683	      std::reverse(__ii, __last);
3684	      return true;
3685	    }
3686	  if (__i == __first)
3687	    {
3688	      std::reverse(__first, __last);
3689	      return false;
3690	    }
3691	}
3692    }
3693
3694  /**
3695   *  @brief  Permute range into the next @e dictionary ordering using
3696   *          comparison functor.
3697   *  @ingroup sorting_algorithms
3698   *  @param  __first  Start of range.
3699   *  @param  __last   End of range.
3700   *  @param  __comp   A comparison functor.
3701   *  @return  False if wrapped to first permutation, true otherwise.
3702   *
3703   *  Treats all permutations of the range [__first,__last) as a set of
3704   *  @e dictionary sorted sequences ordered by @p __comp.  Permutes the current
3705   *  sequence into the next one of this set.  Returns true if there are more
3706   *  sequences to generate.  If the sequence is the largest of the set, the
3707   *  smallest is generated and false returned.
3708  */
3709  template<typename _BidirectionalIterator, typename _Compare>
3710    bool
3711    next_permutation(_BidirectionalIterator __first,
3712		     _BidirectionalIterator __last, _Compare __comp)
3713    {
3714      // concept requirements
3715      __glibcxx_function_requires(_BidirectionalIteratorConcept<
3716				  _BidirectionalIterator>)
3717      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
3718	    typename iterator_traits<_BidirectionalIterator>::value_type,
3719	    typename iterator_traits<_BidirectionalIterator>::value_type>)
3720      __glibcxx_requires_valid_range(__first, __last);
3721
3722      if (__first == __last)
3723	return false;
3724      _BidirectionalIterator __i = __first;
3725      ++__i;
3726      if (__i == __last)
3727	return false;
3728      __i = __last;
3729      --__i;
3730
3731      for(;;)
3732	{
3733	  _BidirectionalIterator __ii = __i;
3734	  --__i;
3735	  if (__comp(*__i, *__ii))
3736	    {
3737	      _BidirectionalIterator __j = __last;
3738	      while (!bool(__comp(*__i, *--__j)))
3739		{}
3740	      std::iter_swap(__i, __j);
3741	      std::reverse(__ii, __last);
3742	      return true;
3743	    }
3744	  if (__i == __first)
3745	    {
3746	      std::reverse(__first, __last);
3747	      return false;
3748	    }
3749	}
3750    }
3751
3752  /**
3753   *  @brief  Permute range into the previous @e dictionary ordering.
3754   *  @ingroup sorting_algorithms
3755   *  @param  __first  Start of range.
3756   *  @param  __last   End of range.
3757   *  @return  False if wrapped to last permutation, true otherwise.
3758   *
3759   *  Treats all permutations of the range as a set of @e dictionary sorted
3760   *  sequences.  Permutes the current sequence into the previous one of this
3761   *  set.  Returns true if there are more sequences to generate.  If the
3762   *  sequence is the smallest of the set, the largest is generated and false
3763   *  returned.
3764  */
3765  template<typename _BidirectionalIterator>
3766    bool
3767    prev_permutation(_BidirectionalIterator __first,
3768		     _BidirectionalIterator __last)
3769    {
3770      // concept requirements
3771      __glibcxx_function_requires(_BidirectionalIteratorConcept<
3772				  _BidirectionalIterator>)
3773      __glibcxx_function_requires(_LessThanComparableConcept<
3774	    typename iterator_traits<_BidirectionalIterator>::value_type>)
3775      __glibcxx_requires_valid_range(__first, __last);
3776
3777      if (__first == __last)
3778	return false;
3779      _BidirectionalIterator __i = __first;
3780      ++__i;
3781      if (__i == __last)
3782	return false;
3783      __i = __last;
3784      --__i;
3785
3786      for(;;)
3787	{
3788	  _BidirectionalIterator __ii = __i;
3789	  --__i;
3790	  if (*__ii < *__i)
3791	    {
3792	      _BidirectionalIterator __j = __last;
3793	      while (!(*--__j < *__i))
3794		{}
3795	      std::iter_swap(__i, __j);
3796	      std::reverse(__ii, __last);
3797	      return true;
3798	    }
3799	  if (__i == __first)
3800	    {
3801	      std::reverse(__first, __last);
3802	      return false;
3803	    }
3804	}
3805    }
3806
3807  /**
3808   *  @brief  Permute range into the previous @e dictionary ordering using
3809   *          comparison functor.
3810   *  @ingroup sorting_algorithms
3811   *  @param  __first  Start of range.
3812   *  @param  __last   End of range.
3813   *  @param  __comp   A comparison functor.
3814   *  @return  False if wrapped to last permutation, true otherwise.
3815   *
3816   *  Treats all permutations of the range [__first,__last) as a set of
3817   *  @e dictionary sorted sequences ordered by @p __comp.  Permutes the current
3818   *  sequence into the previous one of this set.  Returns true if there are
3819   *  more sequences to generate.  If the sequence is the smallest of the set,
3820   *  the largest is generated and false returned.
3821  */
3822  template<typename _BidirectionalIterator, typename _Compare>
3823    bool
3824    prev_permutation(_BidirectionalIterator __first,
3825		     _BidirectionalIterator __last, _Compare __comp)
3826    {
3827      // concept requirements
3828      __glibcxx_function_requires(_BidirectionalIteratorConcept<
3829				  _BidirectionalIterator>)
3830      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
3831	    typename iterator_traits<_BidirectionalIterator>::value_type,
3832	    typename iterator_traits<_BidirectionalIterator>::value_type>)
3833      __glibcxx_requires_valid_range(__first, __last);
3834
3835      if (__first == __last)
3836	return false;
3837      _BidirectionalIterator __i = __first;
3838      ++__i;
3839      if (__i == __last)
3840	return false;
3841      __i = __last;
3842      --__i;
3843
3844      for(;;)
3845	{
3846	  _BidirectionalIterator __ii = __i;
3847	  --__i;
3848	  if (__comp(*__ii, *__i))
3849	    {
3850	      _BidirectionalIterator __j = __last;
3851	      while (!bool(__comp(*--__j, *__i)))
3852		{}
3853	      std::iter_swap(__i, __j);
3854	      std::reverse(__ii, __last);
3855	      return true;
3856	    }
3857	  if (__i == __first)
3858	    {
3859	      std::reverse(__first, __last);
3860	      return false;
3861	    }
3862	}
3863    }
3864
3865  // replace
3866  // replace_if
3867
3868  /**
3869   *  @brief Copy a sequence, replacing each element of one value with another
3870   *         value.
3871   *  @param  __first      An input iterator.
3872   *  @param  __last       An input iterator.
3873   *  @param  __result     An output iterator.
3874   *  @param  __old_value  The value to be replaced.
3875   *  @param  __new_value  The replacement value.
3876   *  @return   The end of the output sequence, @p result+(last-first).
3877   *
3878   *  Copies each element in the input range @p [__first,__last) to the
3879   *  output range @p [__result,__result+(__last-__first)) replacing elements
3880   *  equal to @p __old_value with @p __new_value.
3881  */
3882  template<typename _InputIterator, typename _OutputIterator, typename _Tp>
3883    _OutputIterator
3884    replace_copy(_InputIterator __first, _InputIterator __last,
3885		 _OutputIterator __result,
3886		 const _Tp& __old_value, const _Tp& __new_value)
3887    {
3888      // concept requirements
3889      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
3890      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
3891	    typename iterator_traits<_InputIterator>::value_type>)
3892      __glibcxx_function_requires(_EqualOpConcept<
3893	    typename iterator_traits<_InputIterator>::value_type, _Tp>)
3894      __glibcxx_requires_valid_range(__first, __last);
3895
3896      for (; __first != __last; ++__first, ++__result)
3897	if (*__first == __old_value)
3898	  *__result = __new_value;
3899	else
3900	  *__result = *__first;
3901      return __result;
3902    }
3903
3904  /**
3905   *  @brief Copy a sequence, replacing each value for which a predicate
3906   *         returns true with another value.
3907   *  @ingroup mutating_algorithms
3908   *  @param  __first      An input iterator.
3909   *  @param  __last       An input iterator.
3910   *  @param  __result     An output iterator.
3911   *  @param  __pred       A predicate.
3912   *  @param  __new_value  The replacement value.
3913   *  @return   The end of the output sequence, @p __result+(__last-__first).
3914   *
3915   *  Copies each element in the range @p [__first,__last) to the range
3916   *  @p [__result,__result+(__last-__first)) replacing elements for which
3917   *  @p __pred returns true with @p __new_value.
3918  */
3919  template<typename _InputIterator, typename _OutputIterator,
3920	   typename _Predicate, typename _Tp>
3921    _OutputIterator
3922    replace_copy_if(_InputIterator __first, _InputIterator __last,
3923		    _OutputIterator __result,
3924		    _Predicate __pred, const _Tp& __new_value)
3925    {
3926      // concept requirements
3927      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
3928      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
3929	    typename iterator_traits<_InputIterator>::value_type>)
3930      __glibcxx_function_requires(_UnaryPredicateConcept<_Predicate,
3931	    typename iterator_traits<_InputIterator>::value_type>)
3932      __glibcxx_requires_valid_range(__first, __last);
3933
3934      for (; __first != __last; ++__first, ++__result)
3935	if (__pred(*__first))
3936	  *__result = __new_value;
3937	else
3938	  *__result = *__first;
3939      return __result;
3940    }
3941
3942#if __cplusplus >= 201103L
3943  /**
3944   *  @brief  Determines whether the elements of a sequence are sorted.
3945   *  @ingroup sorting_algorithms
3946   *  @param  __first   An iterator.
3947   *  @param  __last    Another iterator.
3948   *  @return  True if the elements are sorted, false otherwise.
3949  */
3950  template<typename _ForwardIterator>
3951    inline bool
3952    is_sorted(_ForwardIterator __first, _ForwardIterator __last)
3953    { return std::is_sorted_until(__first, __last) == __last; }
3954
3955  /**
3956   *  @brief  Determines whether the elements of a sequence are sorted
3957   *          according to a comparison functor.
3958   *  @ingroup sorting_algorithms
3959   *  @param  __first   An iterator.
3960   *  @param  __last    Another iterator.
3961   *  @param  __comp    A comparison functor.
3962   *  @return  True if the elements are sorted, false otherwise.
3963  */
3964  template<typename _ForwardIterator, typename _Compare>
3965    inline bool
3966    is_sorted(_ForwardIterator __first, _ForwardIterator __last,
3967	      _Compare __comp)
3968    { return std::is_sorted_until(__first, __last, __comp) == __last; }
3969
3970  /**
3971   *  @brief  Determines the end of a sorted sequence.
3972   *  @ingroup sorting_algorithms
3973   *  @param  __first   An iterator.
3974   *  @param  __last    Another iterator.
3975   *  @return  An iterator pointing to the last iterator i in [__first, __last)
3976   *           for which the range [__first, i) is sorted.
3977  */
3978  template<typename _ForwardIterator>
3979    _ForwardIterator
3980    is_sorted_until(_ForwardIterator __first, _ForwardIterator __last)
3981    {
3982      // concept requirements
3983      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
3984      __glibcxx_function_requires(_LessThanComparableConcept<
3985	    typename iterator_traits<_ForwardIterator>::value_type>)
3986      __glibcxx_requires_valid_range(__first, __last);
3987
3988      if (__first == __last)
3989	return __last;
3990
3991      _ForwardIterator __next = __first;
3992      for (++__next; __next != __last; __first = __next, ++__next)
3993	if (*__next < *__first)
3994	  return __next;
3995      return __next;
3996    }
3997
3998  /**
3999   *  @brief  Determines the end of a sorted sequence using comparison functor.
4000   *  @ingroup sorting_algorithms
4001   *  @param  __first   An iterator.
4002   *  @param  __last    Another iterator.
4003   *  @param  __comp    A comparison functor.
4004   *  @return  An iterator pointing to the last iterator i in [__first, __last)
4005   *           for which the range [__first, i) is sorted.
4006  */
4007  template<typename _ForwardIterator, typename _Compare>
4008    _ForwardIterator
4009    is_sorted_until(_ForwardIterator __first, _ForwardIterator __last,
4010		    _Compare __comp)
4011    {
4012      // concept requirements
4013      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
4014      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
4015	    typename iterator_traits<_ForwardIterator>::value_type,
4016	    typename iterator_traits<_ForwardIterator>::value_type>)
4017      __glibcxx_requires_valid_range(__first, __last);
4018
4019      if (__first == __last)
4020	return __last;
4021
4022      _ForwardIterator __next = __first;
4023      for (++__next; __next != __last; __first = __next, ++__next)
4024	if (__comp(*__next, *__first))
4025	  return __next;
4026      return __next;
4027    }
4028
4029  /**
4030   *  @brief  Determines min and max at once as an ordered pair.
4031   *  @ingroup sorting_algorithms
4032   *  @param  __a  A thing of arbitrary type.
4033   *  @param  __b  Another thing of arbitrary type.
4034   *  @return A pair(__b, __a) if __b is smaller than __a, pair(__a,
4035   *  __b) otherwise.
4036  */
4037  template<typename _Tp>
4038    inline pair<const _Tp&, const _Tp&>
4039    minmax(const _Tp& __a, const _Tp& __b)
4040    {
4041      // concept requirements
4042      __glibcxx_function_requires(_LessThanComparableConcept<_Tp>)
4043
4044      return __b < __a ? pair<const _Tp&, const _Tp&>(__b, __a)
4045	               : pair<const _Tp&, const _Tp&>(__a, __b);
4046    }
4047
4048  /**
4049   *  @brief  Determines min and max at once as an ordered pair.
4050   *  @ingroup sorting_algorithms
4051   *  @param  __a  A thing of arbitrary type.
4052   *  @param  __b  Another thing of arbitrary type.
4053   *  @param  __comp  A @link comparison_functors comparison functor @endlink.
4054   *  @return A pair(__b, __a) if __b is smaller than __a, pair(__a,
4055   *  __b) otherwise.
4056  */
4057  template<typename _Tp, typename _Compare>
4058    inline pair<const _Tp&, const _Tp&>
4059    minmax(const _Tp& __a, const _Tp& __b, _Compare __comp)
4060    {
4061      return __comp(__b, __a) ? pair<const _Tp&, const _Tp&>(__b, __a)
4062	                      : pair<const _Tp&, const _Tp&>(__a, __b);
4063    }
4064
4065  /**
4066   *  @brief  Return a pair of iterators pointing to the minimum and maximum
4067   *          elements in a range.
4068   *  @ingroup sorting_algorithms
4069   *  @param  __first  Start of range.
4070   *  @param  __last   End of range.
4071   *  @return  make_pair(m, M), where m is the first iterator i in
4072   *           [__first, __last) such that no other element in the range is
4073   *           smaller, and where M is the last iterator i in [__first, __last)
4074   *           such that no other element in the range is larger.
4075  */
4076  template<typename _ForwardIterator>
4077    pair<_ForwardIterator, _ForwardIterator>
4078    minmax_element(_ForwardIterator __first, _ForwardIterator __last)
4079    {
4080      // concept requirements
4081      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
4082      __glibcxx_function_requires(_LessThanComparableConcept<
4083	    typename iterator_traits<_ForwardIterator>::value_type>)
4084      __glibcxx_requires_valid_range(__first, __last);
4085
4086      _ForwardIterator __next = __first;
4087      if (__first == __last
4088	  || ++__next == __last)
4089	return std::make_pair(__first, __first);
4090
4091      _ForwardIterator __min, __max;
4092      if (*__next < *__first)
4093	{
4094	  __min = __next;
4095	  __max = __first;
4096	}
4097      else
4098	{
4099	  __min = __first;
4100	  __max = __next;
4101	}
4102
4103      __first = __next;
4104      ++__first;
4105
4106      while (__first != __last)
4107	{
4108	  __next = __first;
4109	  if (++__next == __last)
4110	    {
4111	      if (*__first < *__min)
4112		__min = __first;
4113	      else if (!(*__first < *__max))
4114		__max = __first;
4115	      break;
4116	    }
4117
4118	  if (*__next < *__first)
4119	    {
4120	      if (*__next < *__min)
4121		__min = __next;
4122	      if (!(*__first < *__max))
4123		__max = __first;
4124	    }
4125	  else
4126	    {
4127	      if (*__first < *__min)
4128		__min = __first;
4129	      if (!(*__next < *__max))
4130		__max = __next;
4131	    }
4132
4133	  __first = __next;
4134	  ++__first;
4135	}
4136
4137      return std::make_pair(__min, __max);
4138    }
4139
4140  /**
4141   *  @brief  Return a pair of iterators pointing to the minimum and maximum
4142   *          elements in a range.
4143   *  @ingroup sorting_algorithms
4144   *  @param  __first  Start of range.
4145   *  @param  __last   End of range.
4146   *  @param  __comp   Comparison functor.
4147   *  @return  make_pair(m, M), where m is the first iterator i in
4148   *           [__first, __last) such that no other element in the range is
4149   *           smaller, and where M is the last iterator i in [__first, __last)
4150   *           such that no other element in the range is larger.
4151  */
4152  template<typename _ForwardIterator, typename _Compare>
4153    pair<_ForwardIterator, _ForwardIterator>
4154    minmax_element(_ForwardIterator __first, _ForwardIterator __last,
4155		   _Compare __comp)
4156    {
4157      // concept requirements
4158      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
4159      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
4160	    typename iterator_traits<_ForwardIterator>::value_type,
4161	    typename iterator_traits<_ForwardIterator>::value_type>)
4162      __glibcxx_requires_valid_range(__first, __last);
4163
4164      _ForwardIterator __next = __first;
4165      if (__first == __last
4166	  || ++__next == __last)
4167	return std::make_pair(__first, __first);
4168
4169      _ForwardIterator __min, __max;
4170      if (__comp(*__next, *__first))
4171	{
4172	  __min = __next;
4173	  __max = __first;
4174	}
4175      else
4176	{
4177	  __min = __first;
4178	  __max = __next;
4179	}
4180
4181      __first = __next;
4182      ++__first;
4183
4184      while (__first != __last)
4185	{
4186	  __next = __first;
4187	  if (++__next == __last)
4188	    {
4189	      if (__comp(*__first, *__min))
4190		__min = __first;
4191	      else if (!__comp(*__first, *__max))
4192		__max = __first;
4193	      break;
4194	    }
4195
4196	  if (__comp(*__next, *__first))
4197	    {
4198	      if (__comp(*__next, *__min))
4199		__min = __next;
4200	      if (!__comp(*__first, *__max))
4201		__max = __first;
4202	    }
4203	  else
4204	    {
4205	      if (__comp(*__first, *__min))
4206		__min = __first;
4207	      if (!__comp(*__next, *__max))
4208		__max = __next;
4209	    }
4210
4211	  __first = __next;
4212	  ++__first;
4213	}
4214
4215      return std::make_pair(__min, __max);
4216    }
4217
4218  // N2722 + DR 915.
4219  template<typename _Tp>
4220    inline _Tp
4221    min(initializer_list<_Tp> __l)
4222    { return *std::min_element(__l.begin(), __l.end()); }
4223
4224  template<typename _Tp, typename _Compare>
4225    inline _Tp
4226    min(initializer_list<_Tp> __l, _Compare __comp)
4227    { return *std::min_element(__l.begin(), __l.end(), __comp); }
4228
4229  template<typename _Tp>
4230    inline _Tp
4231    max(initializer_list<_Tp> __l)
4232    { return *std::max_element(__l.begin(), __l.end()); }
4233
4234  template<typename _Tp, typename _Compare>
4235    inline _Tp
4236    max(initializer_list<_Tp> __l, _Compare __comp)
4237    { return *std::max_element(__l.begin(), __l.end(), __comp); }
4238
4239  template<typename _Tp>
4240    inline pair<_Tp, _Tp>
4241    minmax(initializer_list<_Tp> __l)
4242    {
4243      pair<const _Tp*, const _Tp*> __p =
4244	std::minmax_element(__l.begin(), __l.end());
4245      return std::make_pair(*__p.first, *__p.second);
4246    }
4247
4248  template<typename _Tp, typename _Compare>
4249    inline pair<_Tp, _Tp>
4250    minmax(initializer_list<_Tp> __l, _Compare __comp)
4251    {
4252      pair<const _Tp*, const _Tp*> __p =
4253	std::minmax_element(__l.begin(), __l.end(), __comp);
4254      return std::make_pair(*__p.first, *__p.second);
4255    }
4256
4257  /**
4258   *  @brief  Checks whether a permutaion of the second sequence is equal
4259   *          to the first sequence.
4260   *  @ingroup non_mutating_algorithms
4261   *  @param  __first1  Start of first range.
4262   *  @param  __last1   End of first range.
4263   *  @param  __first2  Start of second range.
4264   *  @return true if there exists a permutation of the elements in the range
4265   *          [__first2, __first2 + (__last1 - __first1)), beginning with
4266   *          ForwardIterator2 begin, such that equal(__first1, __last1, begin)
4267   *          returns true; otherwise, returns false.
4268  */
4269  template<typename _ForwardIterator1, typename _ForwardIterator2>
4270    bool
4271    is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
4272		   _ForwardIterator2 __first2)
4273    {
4274      // Efficiently compare identical prefixes:  O(N) if sequences
4275      // have the same elements in the same order.
4276      for (; __first1 != __last1; ++__first1, ++__first2)
4277	if (!(*__first1 == *__first2))
4278	  break;
4279
4280      if (__first1 == __last1)
4281	return true;
4282
4283      // Establish __last2 assuming equal ranges by iterating over the
4284      // rest of the list.
4285      _ForwardIterator2 __last2 = __first2;
4286      std::advance(__last2, std::distance(__first1, __last1));
4287      for (_ForwardIterator1 __scan = __first1; __scan != __last1; ++__scan)
4288	{
4289	  if (__scan != _GLIBCXX_STD_A::find(__first1, __scan, *__scan))
4290	    continue; // We've seen this one before.
4291
4292	  auto __matches = std::count(__first2, __last2, *__scan);
4293	  if (0 == __matches
4294	      || std::count(__scan, __last1, *__scan) != __matches)
4295	    return false;
4296	}
4297      return true;
4298    }
4299
4300  /**
4301   *  @brief  Checks whether a permutation of the second sequence is equal
4302   *          to the first sequence.
4303   *  @ingroup non_mutating_algorithms
4304   *  @param  __first1  Start of first range.
4305   *  @param  __last1   End of first range.
4306   *  @param  __first2  Start of second range.
4307   *  @param  __pred    A binary predicate.
4308   *  @return true if there exists a permutation of the elements in
4309   *          the range [__first2, __first2 + (__last1 - __first1)),
4310   *          beginning with ForwardIterator2 begin, such that
4311   *          equal(__first1, __last1, __begin, __pred) returns true;
4312   *          otherwise, returns false.
4313  */
4314  template<typename _ForwardIterator1, typename _ForwardIterator2,
4315	   typename _BinaryPredicate>
4316    bool
4317    is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
4318		   _ForwardIterator2 __first2, _BinaryPredicate __pred)
4319    {
4320      // Efficiently compare identical prefixes:  O(N) if sequences
4321      // have the same elements in the same order.
4322      for (; __first1 != __last1; ++__first1, ++__first2)
4323	if (!bool(__pred(*__first1, *__first2)))
4324	  break;
4325
4326      if (__first1 == __last1)
4327	return true;
4328
4329      // Establish __last2 assuming equal ranges by iterating over the
4330      // rest of the list.
4331      _ForwardIterator2 __last2 = __first2;
4332      std::advance(__last2, std::distance(__first1, __last1));
4333      for (_ForwardIterator1 __scan = __first1; __scan != __last1; ++__scan)
4334	{
4335	  using std::placeholders::_1;
4336
4337	  if (__scan != _GLIBCXX_STD_A::find_if(__first1, __scan,
4338						std::bind(__pred, _1, *__scan)))
4339	    continue; // We've seen this one before.
4340
4341	  auto __matches = std::count_if(__first2, __last2,
4342					 std::bind(__pred, _1, *__scan));
4343	  if (0 == __matches
4344	      || std::count_if(__scan, __last1,
4345			       std::bind(__pred, _1, *__scan)) != __matches)
4346	    return false;
4347	}
4348      return true;
4349    }
4350
4351#ifdef _GLIBCXX_USE_C99_STDINT_TR1
4352  /**
4353   *  @brief Shuffle the elements of a sequence using a uniform random
4354   *         number generator.
4355   *  @ingroup mutating_algorithms
4356   *  @param  __first   A forward iterator.
4357   *  @param  __last    A forward iterator.
4358   *  @param  __g       A UniformRandomNumberGenerator (26.5.1.3).
4359   *  @return  Nothing.
4360   *
4361   *  Reorders the elements in the range @p [__first,__last) using @p __g to
4362   *  provide random numbers.
4363  */
4364  template<typename _RandomAccessIterator,
4365	   typename _UniformRandomNumberGenerator>
4366    void
4367    shuffle(_RandomAccessIterator __first, _RandomAccessIterator __last,
4368	    _UniformRandomNumberGenerator&& __g)
4369    {
4370      // concept requirements
4371      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
4372	    _RandomAccessIterator>)
4373      __glibcxx_requires_valid_range(__first, __last);
4374
4375      if (__first == __last)
4376	return;
4377
4378      typedef typename iterator_traits<_RandomAccessIterator>::difference_type
4379	_DistanceType;
4380
4381      typedef typename std::make_unsigned<_DistanceType>::type __ud_type;
4382      typedef typename std::uniform_int_distribution<__ud_type> __distr_type;
4383      typedef typename __distr_type::param_type __p_type;
4384      __distr_type __d;
4385
4386      for (_RandomAccessIterator __i = __first + 1; __i != __last; ++__i)
4387	std::iter_swap(__i, __first + __d(__g, __p_type(0, __i - __first)));
4388    }
4389#endif
4390
4391#endif // C++11
4392
4393_GLIBCXX_END_NAMESPACE_VERSION
4394
4395_GLIBCXX_BEGIN_NAMESPACE_ALGO
4396
4397  /**
4398   *  @brief Apply a function to every element of a sequence.
4399   *  @ingroup non_mutating_algorithms
4400   *  @param  __first  An input iterator.
4401   *  @param  __last   An input iterator.
4402   *  @param  __f      A unary function object.
4403   *  @return   @p __f (std::move(@p __f) in C++0x).
4404   *
4405   *  Applies the function object @p __f to each element in the range
4406   *  @p [first,last).  @p __f must not modify the order of the sequence.
4407   *  If @p __f has a return value it is ignored.
4408  */
4409  template<typename _InputIterator, typename _Function>
4410    _Function
4411    for_each(_InputIterator __first, _InputIterator __last, _Function __f)
4412    {
4413      // concept requirements
4414      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
4415      __glibcxx_requires_valid_range(__first, __last);
4416      for (; __first != __last; ++__first)
4417	__f(*__first);
4418      return _GLIBCXX_MOVE(__f);
4419    }
4420
4421  /**
4422   *  @brief Find the first occurrence of a value in a sequence.
4423   *  @ingroup non_mutating_algorithms
4424   *  @param  __first  An input iterator.
4425   *  @param  __last   An input iterator.
4426   *  @param  __val    The value to find.
4427   *  @return   The first iterator @c i in the range @p [__first,__last)
4428   *  such that @c *i == @p __val, or @p __last if no such iterator exists.
4429  */
4430  template<typename _InputIterator, typename _Tp>
4431    inline _InputIterator
4432    find(_InputIterator __first, _InputIterator __last,
4433	 const _Tp& __val)
4434    {
4435      // concept requirements
4436      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
4437      __glibcxx_function_requires(_EqualOpConcept<
4438		typename iterator_traits<_InputIterator>::value_type, _Tp>)
4439      __glibcxx_requires_valid_range(__first, __last);
4440      return std::__find(__first, __last, __val,
4441		         std::__iterator_category(__first));
4442    }
4443
4444  /**
4445   *  @brief Find the first element in a sequence for which a
4446   *         predicate is true.
4447   *  @ingroup non_mutating_algorithms
4448   *  @param  __first  An input iterator.
4449   *  @param  __last   An input iterator.
4450   *  @param  __pred   A predicate.
4451   *  @return   The first iterator @c i in the range @p [__first,__last)
4452   *  such that @p __pred(*i) is true, or @p __last if no such iterator exists.
4453  */
4454  template<typename _InputIterator, typename _Predicate>
4455    inline _InputIterator
4456    find_if(_InputIterator __first, _InputIterator __last,
4457	    _Predicate __pred)
4458    {
4459      // concept requirements
4460      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
4461      __glibcxx_function_requires(_UnaryPredicateConcept<_Predicate,
4462	      typename iterator_traits<_InputIterator>::value_type>)
4463      __glibcxx_requires_valid_range(__first, __last);
4464      return std::__find_if(__first, __last, __pred,
4465			    std::__iterator_category(__first));
4466    }
4467
4468  /**
4469   *  @brief  Find element from a set in a sequence.
4470   *  @ingroup non_mutating_algorithms
4471   *  @param  __first1  Start of range to search.
4472   *  @param  __last1   End of range to search.
4473   *  @param  __first2  Start of match candidates.
4474   *  @param  __last2   End of match candidates.
4475   *  @return   The first iterator @c i in the range
4476   *  @p [__first1,__last1) such that @c *i == @p *(i2) such that i2 is an
4477   *  iterator in [__first2,__last2), or @p __last1 if no such iterator exists.
4478   *
4479   *  Searches the range @p [__first1,__last1) for an element that is
4480   *  equal to some element in the range [__first2,__last2).  If
4481   *  found, returns an iterator in the range [__first1,__last1),
4482   *  otherwise returns @p __last1.
4483  */
4484  template<typename _InputIterator, typename _ForwardIterator>
4485    _InputIterator
4486    find_first_of(_InputIterator __first1, _InputIterator __last1,
4487		  _ForwardIterator __first2, _ForwardIterator __last2)
4488    {
4489      // concept requirements
4490      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
4491      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
4492      __glibcxx_function_requires(_EqualOpConcept<
4493	    typename iterator_traits<_InputIterator>::value_type,
4494	    typename iterator_traits<_ForwardIterator>::value_type>)
4495      __glibcxx_requires_valid_range(__first1, __last1);
4496      __glibcxx_requires_valid_range(__first2, __last2);
4497
4498      for (; __first1 != __last1; ++__first1)
4499	for (_ForwardIterator __iter = __first2; __iter != __last2; ++__iter)
4500	  if (*__first1 == *__iter)
4501	    return __first1;
4502      return __last1;
4503    }
4504
4505  /**
4506   *  @brief  Find element from a set in a sequence using a predicate.
4507   *  @ingroup non_mutating_algorithms
4508   *  @param  __first1  Start of range to search.
4509   *  @param  __last1   End of range to search.
4510   *  @param  __first2  Start of match candidates.
4511   *  @param  __last2   End of match candidates.
4512   *  @param  __comp    Predicate to use.
4513   *  @return   The first iterator @c i in the range
4514   *  @p [__first1,__last1) such that @c comp(*i, @p *(i2)) is true
4515   *  and i2 is an iterator in [__first2,__last2), or @p __last1 if no
4516   *  such iterator exists.
4517   *
4518
4519   *  Searches the range @p [__first1,__last1) for an element that is
4520   *  equal to some element in the range [__first2,__last2).  If
4521   *  found, returns an iterator in the range [__first1,__last1),
4522   *  otherwise returns @p __last1.
4523  */
4524  template<typename _InputIterator, typename _ForwardIterator,
4525	   typename _BinaryPredicate>
4526    _InputIterator
4527    find_first_of(_InputIterator __first1, _InputIterator __last1,
4528		  _ForwardIterator __first2, _ForwardIterator __last2,
4529		  _BinaryPredicate __comp)
4530    {
4531      // concept requirements
4532      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
4533      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
4534      __glibcxx_function_requires(_BinaryPredicateConcept<_BinaryPredicate,
4535	    typename iterator_traits<_InputIterator>::value_type,
4536	    typename iterator_traits<_ForwardIterator>::value_type>)
4537      __glibcxx_requires_valid_range(__first1, __last1);
4538      __glibcxx_requires_valid_range(__first2, __last2);
4539
4540      for (; __first1 != __last1; ++__first1)
4541	for (_ForwardIterator __iter = __first2; __iter != __last2; ++__iter)
4542	  if (__comp(*__first1, *__iter))
4543	    return __first1;
4544      return __last1;
4545    }
4546
4547  /**
4548   *  @brief Find two adjacent values in a sequence that are equal.
4549   *  @ingroup non_mutating_algorithms
4550   *  @param  __first  A forward iterator.
4551   *  @param  __last   A forward iterator.
4552   *  @return   The first iterator @c i such that @c i and @c i+1 are both
4553   *  valid iterators in @p [__first,__last) and such that @c *i == @c *(i+1),
4554   *  or @p __last if no such iterator exists.
4555  */
4556  template<typename _ForwardIterator>
4557    _ForwardIterator
4558    adjacent_find(_ForwardIterator __first, _ForwardIterator __last)
4559    {
4560      // concept requirements
4561      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
4562      __glibcxx_function_requires(_EqualityComparableConcept<
4563	    typename iterator_traits<_ForwardIterator>::value_type>)
4564      __glibcxx_requires_valid_range(__first, __last);
4565      if (__first == __last)
4566	return __last;
4567      _ForwardIterator __next = __first;
4568      while(++__next != __last)
4569	{
4570	  if (*__first == *__next)
4571	    return __first;
4572	  __first = __next;
4573	}
4574      return __last;
4575    }
4576
4577  /**
4578   *  @brief Find two adjacent values in a sequence using a predicate.
4579   *  @ingroup non_mutating_algorithms
4580   *  @param  __first         A forward iterator.
4581   *  @param  __last          A forward iterator.
4582   *  @param  __binary_pred   A binary predicate.
4583   *  @return   The first iterator @c i such that @c i and @c i+1 are both
4584   *  valid iterators in @p [__first,__last) and such that
4585   *  @p __binary_pred(*i,*(i+1)) is true, or @p __last if no such iterator
4586   *  exists.
4587  */
4588  template<typename _ForwardIterator, typename _BinaryPredicate>
4589    _ForwardIterator
4590    adjacent_find(_ForwardIterator __first, _ForwardIterator __last,
4591		  _BinaryPredicate __binary_pred)
4592    {
4593      // concept requirements
4594      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
4595      __glibcxx_function_requires(_BinaryPredicateConcept<_BinaryPredicate,
4596	    typename iterator_traits<_ForwardIterator>::value_type,
4597	    typename iterator_traits<_ForwardIterator>::value_type>)
4598      __glibcxx_requires_valid_range(__first, __last);
4599      if (__first == __last)
4600	return __last;
4601      _ForwardIterator __next = __first;
4602      while(++__next != __last)
4603	{
4604	  if (__binary_pred(*__first, *__next))
4605	    return __first;
4606	  __first = __next;
4607	}
4608      return __last;
4609    }
4610
4611  /**
4612   *  @brief Count the number of copies of a value in a sequence.
4613   *  @ingroup non_mutating_algorithms
4614   *  @param  __first  An input iterator.
4615   *  @param  __last   An input iterator.
4616   *  @param  __value  The value to be counted.
4617   *  @return   The number of iterators @c i in the range @p [__first,__last)
4618   *  for which @c *i == @p __value
4619  */
4620  template<typename _InputIterator, typename _Tp>
4621    typename iterator_traits<_InputIterator>::difference_type
4622    count(_InputIterator __first, _InputIterator __last, const _Tp& __value)
4623    {
4624      // concept requirements
4625      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
4626      __glibcxx_function_requires(_EqualOpConcept<
4627	typename iterator_traits<_InputIterator>::value_type, _Tp>)
4628      __glibcxx_requires_valid_range(__first, __last);
4629      typename iterator_traits<_InputIterator>::difference_type __n = 0;
4630      for (; __first != __last; ++__first)
4631	if (*__first == __value)
4632	  ++__n;
4633      return __n;
4634    }
4635
4636  /**
4637   *  @brief Count the elements of a sequence for which a predicate is true.
4638   *  @ingroup non_mutating_algorithms
4639   *  @param  __first  An input iterator.
4640   *  @param  __last   An input iterator.
4641   *  @param  __pred   A predicate.
4642   *  @return   The number of iterators @c i in the range @p [__first,__last)
4643   *  for which @p __pred(*i) is true.
4644  */
4645  template<typename _InputIterator, typename _Predicate>
4646    typename iterator_traits<_InputIterator>::difference_type
4647    count_if(_InputIterator __first, _InputIterator __last, _Predicate __pred)
4648    {
4649      // concept requirements
4650      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
4651      __glibcxx_function_requires(_UnaryPredicateConcept<_Predicate,
4652	    typename iterator_traits<_InputIterator>::value_type>)
4653      __glibcxx_requires_valid_range(__first, __last);
4654      typename iterator_traits<_InputIterator>::difference_type __n = 0;
4655      for (; __first != __last; ++__first)
4656	if (__pred(*__first))
4657	  ++__n;
4658      return __n;
4659    }
4660
4661  /**
4662   *  @brief Search a sequence for a matching sub-sequence.
4663   *  @ingroup non_mutating_algorithms
4664   *  @param  __first1  A forward iterator.
4665   *  @param  __last1   A forward iterator.
4666   *  @param  __first2  A forward iterator.
4667   *  @param  __last2   A forward iterator.
4668   *  @return The first iterator @c i in the range @p
4669   *  [__first1,__last1-(__last2-__first2)) such that @c *(i+N) == @p
4670   *  *(__first2+N) for each @c N in the range @p
4671   *  [0,__last2-__first2), or @p __last1 if no such iterator exists.
4672   *
4673   *  Searches the range @p [__first1,__last1) for a sub-sequence that
4674   *  compares equal value-by-value with the sequence given by @p
4675   *  [__first2,__last2) and returns an iterator to the first element
4676   *  of the sub-sequence, or @p __last1 if the sub-sequence is not
4677   *  found.
4678   *
4679   *  Because the sub-sequence must lie completely within the range @p
4680   *  [__first1,__last1) it must start at a position less than @p
4681   *  __last1-(__last2-__first2) where @p __last2-__first2 is the
4682   *  length of the sub-sequence.
4683   *
4684   *  This means that the returned iterator @c i will be in the range
4685   *  @p [__first1,__last1-(__last2-__first2))
4686  */
4687  template<typename _ForwardIterator1, typename _ForwardIterator2>
4688    _ForwardIterator1
4689    search(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
4690	   _ForwardIterator2 __first2, _ForwardIterator2 __last2)
4691    {
4692      // concept requirements
4693      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator1>)
4694      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator2>)
4695      __glibcxx_function_requires(_EqualOpConcept<
4696	    typename iterator_traits<_ForwardIterator1>::value_type,
4697	    typename iterator_traits<_ForwardIterator2>::value_type>)
4698      __glibcxx_requires_valid_range(__first1, __last1);
4699      __glibcxx_requires_valid_range(__first2, __last2);
4700
4701      // Test for empty ranges
4702      if (__first1 == __last1 || __first2 == __last2)
4703	return __first1;
4704
4705      // Test for a pattern of length 1.
4706      _ForwardIterator2 __p1(__first2);
4707      if (++__p1 == __last2)
4708	return _GLIBCXX_STD_A::find(__first1, __last1, *__first2);
4709
4710      // General case.
4711      _ForwardIterator2 __p;
4712      _ForwardIterator1 __current = __first1;
4713
4714      for (;;)
4715	{
4716	  __first1 = _GLIBCXX_STD_A::find(__first1, __last1, *__first2);
4717	  if (__first1 == __last1)
4718	    return __last1;
4719
4720	  __p = __p1;
4721	  __current = __first1;
4722	  if (++__current == __last1)
4723	    return __last1;
4724
4725	  while (*__current == *__p)
4726	    {
4727	      if (++__p == __last2)
4728		return __first1;
4729	      if (++__current == __last1)
4730		return __last1;
4731	    }
4732	  ++__first1;
4733	}
4734      return __first1;
4735    }
4736
4737  /**
4738   *  @brief Search a sequence for a matching sub-sequence using a predicate.
4739   *  @ingroup non_mutating_algorithms
4740   *  @param  __first1     A forward iterator.
4741   *  @param  __last1      A forward iterator.
4742   *  @param  __first2     A forward iterator.
4743   *  @param  __last2      A forward iterator.
4744   *  @param  __predicate  A binary predicate.
4745   *  @return   The first iterator @c i in the range
4746   *  @p [__first1,__last1-(__last2-__first2)) such that
4747   *  @p __predicate(*(i+N),*(__first2+N)) is true for each @c N in the range
4748   *  @p [0,__last2-__first2), or @p __last1 if no such iterator exists.
4749   *
4750   *  Searches the range @p [__first1,__last1) for a sub-sequence that
4751   *  compares equal value-by-value with the sequence given by @p
4752   *  [__first2,__last2), using @p __predicate to determine equality,
4753   *  and returns an iterator to the first element of the
4754   *  sub-sequence, or @p __last1 if no such iterator exists.
4755   *
4756   *  @see search(_ForwardIter1, _ForwardIter1, _ForwardIter2, _ForwardIter2)
4757  */
4758  template<typename _ForwardIterator1, typename _ForwardIterator2,
4759	   typename _BinaryPredicate>
4760    _ForwardIterator1
4761    search(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
4762	   _ForwardIterator2 __first2, _ForwardIterator2 __last2,
4763	   _BinaryPredicate  __predicate)
4764    {
4765      // concept requirements
4766      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator1>)
4767      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator2>)
4768      __glibcxx_function_requires(_BinaryPredicateConcept<_BinaryPredicate,
4769	    typename iterator_traits<_ForwardIterator1>::value_type,
4770	    typename iterator_traits<_ForwardIterator2>::value_type>)
4771      __glibcxx_requires_valid_range(__first1, __last1);
4772      __glibcxx_requires_valid_range(__first2, __last2);
4773
4774      // Test for empty ranges
4775      if (__first1 == __last1 || __first2 == __last2)
4776	return __first1;
4777
4778      // Test for a pattern of length 1.
4779      _ForwardIterator2 __p1(__first2);
4780      if (++__p1 == __last2)
4781	{
4782	  while (__first1 != __last1
4783		 && !bool(__predicate(*__first1, *__first2)))
4784	    ++__first1;
4785	  return __first1;
4786	}
4787
4788      // General case.
4789      _ForwardIterator2 __p;
4790      _ForwardIterator1 __current = __first1;
4791
4792      for (;;)
4793	{
4794	  while (__first1 != __last1
4795		 && !bool(__predicate(*__first1, *__first2)))
4796	    ++__first1;
4797	  if (__first1 == __last1)
4798	    return __last1;
4799
4800	  __p = __p1;
4801	  __current = __first1;
4802	  if (++__current == __last1)
4803	    return __last1;
4804
4805	  while (__predicate(*__current, *__p))
4806	    {
4807	      if (++__p == __last2)
4808		return __first1;
4809	      if (++__current == __last1)
4810		return __last1;
4811	    }
4812	  ++__first1;
4813	}
4814      return __first1;
4815    }
4816
4817
4818  /**
4819   *  @brief Search a sequence for a number of consecutive values.
4820   *  @ingroup non_mutating_algorithms
4821   *  @param  __first  A forward iterator.
4822   *  @param  __last   A forward iterator.
4823   *  @param  __count  The number of consecutive values.
4824   *  @param  __val    The value to find.
4825   *  @return The first iterator @c i in the range @p
4826   *  [__first,__last-__count) such that @c *(i+N) == @p __val for
4827   *  each @c N in the range @p [0,__count), or @p __last if no such
4828   *  iterator exists.
4829   *
4830   *  Searches the range @p [__first,__last) for @p count consecutive elements
4831   *  equal to @p __val.
4832  */
4833  template<typename _ForwardIterator, typename _Integer, typename _Tp>
4834    _ForwardIterator
4835    search_n(_ForwardIterator __first, _ForwardIterator __last,
4836	     _Integer __count, const _Tp& __val)
4837    {
4838      // concept requirements
4839      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
4840      __glibcxx_function_requires(_EqualOpConcept<
4841	typename iterator_traits<_ForwardIterator>::value_type, _Tp>)
4842      __glibcxx_requires_valid_range(__first, __last);
4843
4844      if (__count <= 0)
4845	return __first;
4846      if (__count == 1)
4847	return _GLIBCXX_STD_A::find(__first, __last, __val);
4848      return std::__search_n(__first, __last, __count, __val,
4849			     std::__iterator_category(__first));
4850    }
4851
4852
4853  /**
4854   *  @brief Search a sequence for a number of consecutive values using a
4855   *         predicate.
4856   *  @ingroup non_mutating_algorithms
4857   *  @param  __first        A forward iterator.
4858   *  @param  __last         A forward iterator.
4859   *  @param  __count        The number of consecutive values.
4860   *  @param  __val          The value to find.
4861   *  @param  __binary_pred  A binary predicate.
4862   *  @return The first iterator @c i in the range @p
4863   *  [__first,__last-__count) such that @p
4864   *  __binary_pred(*(i+N),__val) is true for each @c N in the range
4865   *  @p [0,__count), or @p __last if no such iterator exists.
4866   *
4867   *  Searches the range @p [__first,__last) for @p __count
4868   *  consecutive elements for which the predicate returns true.
4869  */
4870  template<typename _ForwardIterator, typename _Integer, typename _Tp,
4871           typename _BinaryPredicate>
4872    _ForwardIterator
4873    search_n(_ForwardIterator __first, _ForwardIterator __last,
4874	     _Integer __count, const _Tp& __val,
4875	     _BinaryPredicate __binary_pred)
4876    {
4877      // concept requirements
4878      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
4879      __glibcxx_function_requires(_BinaryPredicateConcept<_BinaryPredicate,
4880	    typename iterator_traits<_ForwardIterator>::value_type, _Tp>)
4881      __glibcxx_requires_valid_range(__first, __last);
4882
4883      if (__count <= 0)
4884	return __first;
4885      if (__count == 1)
4886	{
4887	  while (__first != __last && !bool(__binary_pred(*__first, __val)))
4888	    ++__first;
4889	  return __first;
4890	}
4891      return std::__search_n(__first, __last, __count, __val, __binary_pred,
4892			     std::__iterator_category(__first));
4893    }
4894
4895
4896  /**
4897   *  @brief Perform an operation on a sequence.
4898   *  @ingroup mutating_algorithms
4899   *  @param  __first     An input iterator.
4900   *  @param  __last      An input iterator.
4901   *  @param  __result    An output iterator.
4902   *  @param  __unary_op  A unary operator.
4903   *  @return   An output iterator equal to @p __result+(__last-__first).
4904   *
4905   *  Applies the operator to each element in the input range and assigns
4906   *  the results to successive elements of the output sequence.
4907   *  Evaluates @p *(__result+N)=unary_op(*(__first+N)) for each @c N in the
4908   *  range @p [0,__last-__first).
4909   *
4910   *  @p unary_op must not alter its argument.
4911  */
4912  template<typename _InputIterator, typename _OutputIterator,
4913	   typename _UnaryOperation>
4914    _OutputIterator
4915    transform(_InputIterator __first, _InputIterator __last,
4916	      _OutputIterator __result, _UnaryOperation __unary_op)
4917    {
4918      // concept requirements
4919      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
4920      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
4921            // "the type returned by a _UnaryOperation"
4922            __typeof__(__unary_op(*__first))>)
4923      __glibcxx_requires_valid_range(__first, __last);
4924
4925      for (; __first != __last; ++__first, ++__result)
4926	*__result = __unary_op(*__first);
4927      return __result;
4928    }
4929
4930  /**
4931   *  @brief Perform an operation on corresponding elements of two sequences.
4932   *  @ingroup mutating_algorithms
4933   *  @param  __first1     An input iterator.
4934   *  @param  __last1      An input iterator.
4935   *  @param  __first2     An input iterator.
4936   *  @param  __result     An output iterator.
4937   *  @param  __binary_op  A binary operator.
4938   *  @return   An output iterator equal to @p result+(last-first).
4939   *
4940   *  Applies the operator to the corresponding elements in the two
4941   *  input ranges and assigns the results to successive elements of the
4942   *  output sequence.
4943   *  Evaluates @p
4944   *  *(__result+N)=__binary_op(*(__first1+N),*(__first2+N)) for each
4945   *  @c N in the range @p [0,__last1-__first1).
4946   *
4947   *  @p binary_op must not alter either of its arguments.
4948  */
4949  template<typename _InputIterator1, typename _InputIterator2,
4950	   typename _OutputIterator, typename _BinaryOperation>
4951    _OutputIterator
4952    transform(_InputIterator1 __first1, _InputIterator1 __last1,
4953	      _InputIterator2 __first2, _OutputIterator __result,
4954	      _BinaryOperation __binary_op)
4955    {
4956      // concept requirements
4957      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
4958      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
4959      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
4960            // "the type returned by a _BinaryOperation"
4961            __typeof__(__binary_op(*__first1,*__first2))>)
4962      __glibcxx_requires_valid_range(__first1, __last1);
4963
4964      for (; __first1 != __last1; ++__first1, ++__first2, ++__result)
4965	*__result = __binary_op(*__first1, *__first2);
4966      return __result;
4967    }
4968
4969  /**
4970   *  @brief Replace each occurrence of one value in a sequence with another
4971   *         value.
4972   *  @ingroup mutating_algorithms
4973   *  @param  __first      A forward iterator.
4974   *  @param  __last       A forward iterator.
4975   *  @param  __old_value  The value to be replaced.
4976   *  @param  __new_value  The replacement value.
4977   *  @return   replace() returns no value.
4978   *
4979   *  For each iterator @c i in the range @p [__first,__last) if @c *i ==
4980   *  @p __old_value then the assignment @c *i = @p __new_value is performed.
4981  */
4982  template<typename _ForwardIterator, typename _Tp>
4983    void
4984    replace(_ForwardIterator __first, _ForwardIterator __last,
4985	    const _Tp& __old_value, const _Tp& __new_value)
4986    {
4987      // concept requirements
4988      __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<
4989				  _ForwardIterator>)
4990      __glibcxx_function_requires(_EqualOpConcept<
4991	    typename iterator_traits<_ForwardIterator>::value_type, _Tp>)
4992      __glibcxx_function_requires(_ConvertibleConcept<_Tp,
4993	    typename iterator_traits<_ForwardIterator>::value_type>)
4994      __glibcxx_requires_valid_range(__first, __last);
4995
4996      for (; __first != __last; ++__first)
4997	if (*__first == __old_value)
4998	  *__first = __new_value;
4999    }
5000
5001  /**
5002   *  @brief Replace each value in a sequence for which a predicate returns
5003   *         true with another value.
5004   *  @ingroup mutating_algorithms
5005   *  @param  __first      A forward iterator.
5006   *  @param  __last       A forward iterator.
5007   *  @param  __pred       A predicate.
5008   *  @param  __new_value  The replacement value.
5009   *  @return   replace_if() returns no value.
5010   *
5011   *  For each iterator @c i in the range @p [__first,__last) if @p __pred(*i)
5012   *  is true then the assignment @c *i = @p __new_value is performed.
5013  */
5014  template<typename _ForwardIterator, typename _Predicate, typename _Tp>
5015    void
5016    replace_if(_ForwardIterator __first, _ForwardIterator __last,
5017	       _Predicate __pred, const _Tp& __new_value)
5018    {
5019      // concept requirements
5020      __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<
5021				  _ForwardIterator>)
5022      __glibcxx_function_requires(_ConvertibleConcept<_Tp,
5023	    typename iterator_traits<_ForwardIterator>::value_type>)
5024      __glibcxx_function_requires(_UnaryPredicateConcept<_Predicate,
5025	    typename iterator_traits<_ForwardIterator>::value_type>)
5026      __glibcxx_requires_valid_range(__first, __last);
5027
5028      for (; __first != __last; ++__first)
5029	if (__pred(*__first))
5030	  *__first = __new_value;
5031    }
5032
5033  /**
5034   *  @brief Assign the result of a function object to each value in a
5035   *         sequence.
5036   *  @ingroup mutating_algorithms
5037   *  @param  __first  A forward iterator.
5038   *  @param  __last   A forward iterator.
5039   *  @param  __gen    A function object taking no arguments and returning
5040   *                 std::iterator_traits<_ForwardIterator>::value_type
5041   *  @return   generate() returns no value.
5042   *
5043   *  Performs the assignment @c *i = @p __gen() for each @c i in the range
5044   *  @p [__first,__last).
5045  */
5046  template<typename _ForwardIterator, typename _Generator>
5047    void
5048    generate(_ForwardIterator __first, _ForwardIterator __last,
5049	     _Generator __gen)
5050    {
5051      // concept requirements
5052      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
5053      __glibcxx_function_requires(_GeneratorConcept<_Generator,
5054	    typename iterator_traits<_ForwardIterator>::value_type>)
5055      __glibcxx_requires_valid_range(__first, __last);
5056
5057      for (; __first != __last; ++__first)
5058	*__first = __gen();
5059    }
5060
5061  /**
5062   *  @brief Assign the result of a function object to each value in a
5063   *         sequence.
5064   *  @ingroup mutating_algorithms
5065   *  @param  __first  A forward iterator.
5066   *  @param  __n      The length of the sequence.
5067   *  @param  __gen    A function object taking no arguments and returning
5068   *                 std::iterator_traits<_ForwardIterator>::value_type
5069   *  @return   The end of the sequence, @p __first+__n
5070   *
5071   *  Performs the assignment @c *i = @p __gen() for each @c i in the range
5072   *  @p [__first,__first+__n).
5073   *
5074   *  _GLIBCXX_RESOLVE_LIB_DEFECTS
5075   *  DR 865. More algorithms that throw away information
5076  */
5077  template<typename _OutputIterator, typename _Size, typename _Generator>
5078    _OutputIterator
5079    generate_n(_OutputIterator __first, _Size __n, _Generator __gen)
5080    {
5081      // concept requirements
5082      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
5083            // "the type returned by a _Generator"
5084            __typeof__(__gen())>)
5085
5086      for (__decltype(__n + 0) __niter = __n;
5087	   __niter > 0; --__niter, ++__first)
5088	*__first = __gen();
5089      return __first;
5090    }
5091
5092
5093  /**
5094   *  @brief Copy a sequence, removing consecutive duplicate values.
5095   *  @ingroup mutating_algorithms
5096   *  @param  __first   An input iterator.
5097   *  @param  __last    An input iterator.
5098   *  @param  __result  An output iterator.
5099   *  @return   An iterator designating the end of the resulting sequence.
5100   *
5101   *  Copies each element in the range @p [__first,__last) to the range
5102   *  beginning at @p __result, except that only the first element is copied
5103   *  from groups of consecutive elements that compare equal.
5104   *  unique_copy() is stable, so the relative order of elements that are
5105   *  copied is unchanged.
5106   *
5107   *  _GLIBCXX_RESOLVE_LIB_DEFECTS
5108   *  DR 241. Does unique_copy() require CopyConstructible and Assignable?
5109   *
5110   *  _GLIBCXX_RESOLVE_LIB_DEFECTS
5111   *  DR 538. 241 again: Does unique_copy() require CopyConstructible and
5112   *  Assignable?
5113  */
5114  template<typename _InputIterator, typename _OutputIterator>
5115    inline _OutputIterator
5116    unique_copy(_InputIterator __first, _InputIterator __last,
5117		_OutputIterator __result)
5118    {
5119      // concept requirements
5120      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
5121      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
5122	    typename iterator_traits<_InputIterator>::value_type>)
5123      __glibcxx_function_requires(_EqualityComparableConcept<
5124	    typename iterator_traits<_InputIterator>::value_type>)
5125      __glibcxx_requires_valid_range(__first, __last);
5126
5127      if (__first == __last)
5128	return __result;
5129      return std::__unique_copy(__first, __last, __result,
5130				std::__iterator_category(__first),
5131				std::__iterator_category(__result));
5132    }
5133
5134  /**
5135   *  @brief Copy a sequence, removing consecutive values using a predicate.
5136   *  @ingroup mutating_algorithms
5137   *  @param  __first        An input iterator.
5138   *  @param  __last         An input iterator.
5139   *  @param  __result       An output iterator.
5140   *  @param  __binary_pred  A binary predicate.
5141   *  @return   An iterator designating the end of the resulting sequence.
5142   *
5143   *  Copies each element in the range @p [__first,__last) to the range
5144   *  beginning at @p __result, except that only the first element is copied
5145   *  from groups of consecutive elements for which @p __binary_pred returns
5146   *  true.
5147   *  unique_copy() is stable, so the relative order of elements that are
5148   *  copied is unchanged.
5149   *
5150   *  _GLIBCXX_RESOLVE_LIB_DEFECTS
5151   *  DR 241. Does unique_copy() require CopyConstructible and Assignable?
5152  */
5153  template<typename _InputIterator, typename _OutputIterator,
5154	   typename _BinaryPredicate>
5155    inline _OutputIterator
5156    unique_copy(_InputIterator __first, _InputIterator __last,
5157		_OutputIterator __result,
5158		_BinaryPredicate __binary_pred)
5159    {
5160      // concept requirements -- predicates checked later
5161      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
5162      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
5163	    typename iterator_traits<_InputIterator>::value_type>)
5164      __glibcxx_requires_valid_range(__first, __last);
5165
5166      if (__first == __last)
5167	return __result;
5168      return std::__unique_copy(__first, __last, __result, __binary_pred,
5169				std::__iterator_category(__first),
5170				std::__iterator_category(__result));
5171    }
5172
5173
5174  /**
5175   *  @brief Randomly shuffle the elements of a sequence.
5176   *  @ingroup mutating_algorithms
5177   *  @param  __first   A forward iterator.
5178   *  @param  __last    A forward iterator.
5179   *  @return  Nothing.
5180   *
5181   *  Reorder the elements in the range @p [__first,__last) using a random
5182   *  distribution, so that every possible ordering of the sequence is
5183   *  equally likely.
5184  */
5185  template<typename _RandomAccessIterator>
5186    inline void
5187    random_shuffle(_RandomAccessIterator __first, _RandomAccessIterator __last)
5188    {
5189      // concept requirements
5190      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
5191	    _RandomAccessIterator>)
5192      __glibcxx_requires_valid_range(__first, __last);
5193
5194      if (__first != __last)
5195	for (_RandomAccessIterator __i = __first + 1; __i != __last; ++__i)
5196	  std::iter_swap(__i, __first + (std::rand() % ((__i - __first) + 1)));
5197    }
5198
5199  /**
5200   *  @brief Shuffle the elements of a sequence using a random number
5201   *         generator.
5202   *  @ingroup mutating_algorithms
5203   *  @param  __first   A forward iterator.
5204   *  @param  __last    A forward iterator.
5205   *  @param  __rand    The RNG functor or function.
5206   *  @return  Nothing.
5207   *
5208   *  Reorders the elements in the range @p [__first,__last) using @p __rand to
5209   *  provide a random distribution. Calling @p __rand(N) for a positive
5210   *  integer @p N should return a randomly chosen integer from the
5211   *  range [0,N).
5212  */
5213  template<typename _RandomAccessIterator, typename _RandomNumberGenerator>
5214    void
5215    random_shuffle(_RandomAccessIterator __first, _RandomAccessIterator __last,
5216#if __cplusplus >= 201103L
5217		   _RandomNumberGenerator&& __rand)
5218#else
5219		   _RandomNumberGenerator& __rand)
5220#endif
5221    {
5222      // concept requirements
5223      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
5224	    _RandomAccessIterator>)
5225      __glibcxx_requires_valid_range(__first, __last);
5226
5227      if (__first == __last)
5228	return;
5229      for (_RandomAccessIterator __i = __first + 1; __i != __last; ++__i)
5230	std::iter_swap(__i, __first + __rand((__i - __first) + 1));
5231    }
5232
5233
5234  /**
5235   *  @brief Move elements for which a predicate is true to the beginning
5236   *         of a sequence.
5237   *  @ingroup mutating_algorithms
5238   *  @param  __first   A forward iterator.
5239   *  @param  __last    A forward iterator.
5240   *  @param  __pred    A predicate functor.
5241   *  @return  An iterator @p middle such that @p __pred(i) is true for each
5242   *  iterator @p i in the range @p [__first,middle) and false for each @p i
5243   *  in the range @p [middle,__last).
5244   *
5245   *  @p __pred must not modify its operand. @p partition() does not preserve
5246   *  the relative ordering of elements in each group, use
5247   *  @p stable_partition() if this is needed.
5248  */
5249  template<typename _ForwardIterator, typename _Predicate>
5250    inline _ForwardIterator
5251    partition(_ForwardIterator __first, _ForwardIterator __last,
5252	      _Predicate   __pred)
5253    {
5254      // concept requirements
5255      __glibcxx_function_requires(_Mutable_ForwardIteratorConcept<
5256				  _ForwardIterator>)
5257      __glibcxx_function_requires(_UnaryPredicateConcept<_Predicate,
5258	    typename iterator_traits<_ForwardIterator>::value_type>)
5259      __glibcxx_requires_valid_range(__first, __last);
5260
5261      return std::__partition(__first, __last, __pred,
5262			      std::__iterator_category(__first));
5263    }
5264
5265
5266
5267  /**
5268   *  @brief Sort the smallest elements of a sequence.
5269   *  @ingroup sorting_algorithms
5270   *  @param  __first   An iterator.
5271   *  @param  __middle  Another iterator.
5272   *  @param  __last    Another iterator.
5273   *  @return  Nothing.
5274   *
5275   *  Sorts the smallest @p (__middle-__first) elements in the range
5276   *  @p [first,last) and moves them to the range @p [__first,__middle). The
5277   *  order of the remaining elements in the range @p [__middle,__last) is
5278   *  undefined.
5279   *  After the sort if @e i and @e j are iterators in the range
5280   *  @p [__first,__middle) such that i precedes j and @e k is an iterator in
5281   *  the range @p [__middle,__last) then *j<*i and *k<*i are both false.
5282  */
5283  template<typename _RandomAccessIterator>
5284    inline void
5285    partial_sort(_RandomAccessIterator __first,
5286		 _RandomAccessIterator __middle,
5287		 _RandomAccessIterator __last)
5288    {
5289      typedef typename iterator_traits<_RandomAccessIterator>::value_type
5290	_ValueType;
5291
5292      // concept requirements
5293      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
5294	    _RandomAccessIterator>)
5295      __glibcxx_function_requires(_LessThanComparableConcept<_ValueType>)
5296      __glibcxx_requires_valid_range(__first, __middle);
5297      __glibcxx_requires_valid_range(__middle, __last);
5298
5299      std::__heap_select(__first, __middle, __last);
5300      std::sort_heap(__first, __middle);
5301    }
5302
5303  /**
5304   *  @brief Sort the smallest elements of a sequence using a predicate
5305   *         for comparison.
5306   *  @ingroup sorting_algorithms
5307   *  @param  __first   An iterator.
5308   *  @param  __middle  Another iterator.
5309   *  @param  __last    Another iterator.
5310   *  @param  __comp    A comparison functor.
5311   *  @return  Nothing.
5312   *
5313   *  Sorts the smallest @p (__middle-__first) elements in the range
5314   *  @p [__first,__last) and moves them to the range @p [__first,__middle). The
5315   *  order of the remaining elements in the range @p [__middle,__last) is
5316   *  undefined.
5317   *  After the sort if @e i and @e j are iterators in the range
5318   *  @p [__first,__middle) such that i precedes j and @e k is an iterator in
5319   *  the range @p [__middle,__last) then @p *__comp(j,*i) and @p __comp(*k,*i)
5320   *  are both false.
5321  */
5322  template<typename _RandomAccessIterator, typename _Compare>
5323    inline void
5324    partial_sort(_RandomAccessIterator __first,
5325		 _RandomAccessIterator __middle,
5326		 _RandomAccessIterator __last,
5327		 _Compare __comp)
5328    {
5329      typedef typename iterator_traits<_RandomAccessIterator>::value_type
5330	_ValueType;
5331
5332      // concept requirements
5333      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
5334	    _RandomAccessIterator>)
5335      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
5336				  _ValueType, _ValueType>)
5337      __glibcxx_requires_valid_range(__first, __middle);
5338      __glibcxx_requires_valid_range(__middle, __last);
5339
5340      std::__heap_select(__first, __middle, __last, __comp);
5341      std::sort_heap(__first, __middle, __comp);
5342    }
5343
5344  /**
5345   *  @brief Sort a sequence just enough to find a particular position.
5346   *  @ingroup sorting_algorithms
5347   *  @param  __first   An iterator.
5348   *  @param  __nth     Another iterator.
5349   *  @param  __last    Another iterator.
5350   *  @return  Nothing.
5351   *
5352   *  Rearranges the elements in the range @p [__first,__last) so that @p *__nth
5353   *  is the same element that would have been in that position had the
5354   *  whole sequence been sorted. The elements either side of @p *__nth are
5355   *  not completely sorted, but for any iterator @e i in the range
5356   *  @p [__first,__nth) and any iterator @e j in the range @p [__nth,__last) it
5357   *  holds that *j < *i is false.
5358  */
5359  template<typename _RandomAccessIterator>
5360    inline void
5361    nth_element(_RandomAccessIterator __first, _RandomAccessIterator __nth,
5362		_RandomAccessIterator __last)
5363    {
5364      typedef typename iterator_traits<_RandomAccessIterator>::value_type
5365	_ValueType;
5366
5367      // concept requirements
5368      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
5369				  _RandomAccessIterator>)
5370      __glibcxx_function_requires(_LessThanComparableConcept<_ValueType>)
5371      __glibcxx_requires_valid_range(__first, __nth);
5372      __glibcxx_requires_valid_range(__nth, __last);
5373
5374      if (__first == __last || __nth == __last)
5375	return;
5376
5377      std::__introselect(__first, __nth, __last,
5378			 std::__lg(__last - __first) * 2);
5379    }
5380
5381  /**
5382   *  @brief Sort a sequence just enough to find a particular position
5383   *         using a predicate for comparison.
5384   *  @ingroup sorting_algorithms
5385   *  @param  __first   An iterator.
5386   *  @param  __nth     Another iterator.
5387   *  @param  __last    Another iterator.
5388   *  @param  __comp    A comparison functor.
5389   *  @return  Nothing.
5390   *
5391   *  Rearranges the elements in the range @p [__first,__last) so that @p *__nth
5392   *  is the same element that would have been in that position had the
5393   *  whole sequence been sorted. The elements either side of @p *__nth are
5394   *  not completely sorted, but for any iterator @e i in the range
5395   *  @p [__first,__nth) and any iterator @e j in the range @p [__nth,__last) it
5396   *  holds that @p __comp(*j,*i) is false.
5397  */
5398  template<typename _RandomAccessIterator, typename _Compare>
5399    inline void
5400    nth_element(_RandomAccessIterator __first, _RandomAccessIterator __nth,
5401		_RandomAccessIterator __last, _Compare __comp)
5402    {
5403      typedef typename iterator_traits<_RandomAccessIterator>::value_type
5404	_ValueType;
5405
5406      // concept requirements
5407      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
5408				  _RandomAccessIterator>)
5409      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
5410				  _ValueType, _ValueType>)
5411      __glibcxx_requires_valid_range(__first, __nth);
5412      __glibcxx_requires_valid_range(__nth, __last);
5413
5414      if (__first == __last || __nth == __last)
5415	return;
5416
5417      std::__introselect(__first, __nth, __last,
5418			 std::__lg(__last - __first) * 2, __comp);
5419    }
5420
5421
5422  /**
5423   *  @brief Sort the elements of a sequence.
5424   *  @ingroup sorting_algorithms
5425   *  @param  __first   An iterator.
5426   *  @param  __last    Another iterator.
5427   *  @return  Nothing.
5428   *
5429   *  Sorts the elements in the range @p [__first,__last) in ascending order,
5430   *  such that for each iterator @e i in the range @p [__first,__last-1),
5431   *  *(i+1)<*i is false.
5432   *
5433   *  The relative ordering of equivalent elements is not preserved, use
5434   *  @p stable_sort() if this is needed.
5435  */
5436  template<typename _RandomAccessIterator>
5437    inline void
5438    sort(_RandomAccessIterator __first, _RandomAccessIterator __last)
5439    {
5440      typedef typename iterator_traits<_RandomAccessIterator>::value_type
5441	_ValueType;
5442
5443      // concept requirements
5444      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
5445	    _RandomAccessIterator>)
5446      __glibcxx_function_requires(_LessThanComparableConcept<_ValueType>)
5447      __glibcxx_requires_valid_range(__first, __last);
5448
5449      if (__first != __last)
5450	{
5451	  std::__introsort_loop(__first, __last,
5452				std::__lg(__last - __first) * 2);
5453	  std::__final_insertion_sort(__first, __last);
5454	}
5455    }
5456
5457  /**
5458   *  @brief Sort the elements of a sequence using a predicate for comparison.
5459   *  @ingroup sorting_algorithms
5460   *  @param  __first   An iterator.
5461   *  @param  __last    Another iterator.
5462   *  @param  __comp    A comparison functor.
5463   *  @return  Nothing.
5464   *
5465   *  Sorts the elements in the range @p [__first,__last) in ascending order,
5466   *  such that @p __comp(*(i+1),*i) is false for every iterator @e i in the
5467   *  range @p [__first,__last-1).
5468   *
5469   *  The relative ordering of equivalent elements is not preserved, use
5470   *  @p stable_sort() if this is needed.
5471  */
5472  template<typename _RandomAccessIterator, typename _Compare>
5473    inline void
5474    sort(_RandomAccessIterator __first, _RandomAccessIterator __last,
5475	 _Compare __comp)
5476    {
5477      typedef typename iterator_traits<_RandomAccessIterator>::value_type
5478	_ValueType;
5479
5480      // concept requirements
5481      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
5482	    _RandomAccessIterator>)
5483      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare, _ValueType,
5484				  _ValueType>)
5485      __glibcxx_requires_valid_range(__first, __last);
5486
5487      if (__first != __last)
5488	{
5489	  std::__introsort_loop(__first, __last,
5490				std::__lg(__last - __first) * 2, __comp);
5491	  std::__final_insertion_sort(__first, __last, __comp);
5492	}
5493    }
5494
5495  /**
5496   *  @brief Merges two sorted ranges.
5497   *  @ingroup sorting_algorithms
5498   *  @param  __first1  An iterator.
5499   *  @param  __first2  Another iterator.
5500   *  @param  __last1   Another iterator.
5501   *  @param  __last2   Another iterator.
5502   *  @param  __result  An iterator pointing to the end of the merged range.
5503   *  @return         An iterator pointing to the first element <em>not less
5504   *                  than</em> @e val.
5505   *
5506   *  Merges the ranges @p [__first1,__last1) and @p [__first2,__last2) into
5507   *  the sorted range @p [__result, __result + (__last1-__first1) +
5508   *  (__last2-__first2)).  Both input ranges must be sorted, and the
5509   *  output range must not overlap with either of the input ranges.
5510   *  The sort is @e stable, that is, for equivalent elements in the
5511   *  two ranges, elements from the first range will always come
5512   *  before elements from the second.
5513  */
5514  template<typename _InputIterator1, typename _InputIterator2,
5515	   typename _OutputIterator>
5516    _OutputIterator
5517    merge(_InputIterator1 __first1, _InputIterator1 __last1,
5518	  _InputIterator2 __first2, _InputIterator2 __last2,
5519	  _OutputIterator __result)
5520    {
5521      typedef typename iterator_traits<_InputIterator1>::value_type
5522	_ValueType1;
5523      typedef typename iterator_traits<_InputIterator2>::value_type
5524	_ValueType2;
5525
5526      // concept requirements
5527      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
5528      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
5529      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
5530				  _ValueType1>)
5531      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
5532				  _ValueType2>)
5533      __glibcxx_function_requires(_LessThanOpConcept<_ValueType2, _ValueType1>)
5534      __glibcxx_requires_sorted_set(__first1, __last1, __first2);
5535      __glibcxx_requires_sorted_set(__first2, __last2, __first1);
5536
5537      while (__first1 != __last1 && __first2 != __last2)
5538	{
5539	  if (*__first2 < *__first1)
5540	    {
5541	      *__result = *__first2;
5542	      ++__first2;
5543	    }
5544	  else
5545	    {
5546	      *__result = *__first1;
5547	      ++__first1;
5548	    }
5549	  ++__result;
5550	}
5551      return std::copy(__first2, __last2, std::copy(__first1, __last1,
5552						    __result));
5553    }
5554
5555  /**
5556   *  @brief Merges two sorted ranges.
5557   *  @ingroup sorting_algorithms
5558   *  @param  __first1  An iterator.
5559   *  @param  __first2  Another iterator.
5560   *  @param  __last1   Another iterator.
5561   *  @param  __last2   Another iterator.
5562   *  @param  __result  An iterator pointing to the end of the merged range.
5563   *  @param  __comp    A functor to use for comparisons.
5564   *  @return         An iterator pointing to the first element "not less
5565   *                  than" @e val.
5566   *
5567   *  Merges the ranges @p [__first1,__last1) and @p [__first2,__last2) into
5568   *  the sorted range @p [__result, __result + (__last1-__first1) +
5569   *  (__last2-__first2)).  Both input ranges must be sorted, and the
5570   *  output range must not overlap with either of the input ranges.
5571   *  The sort is @e stable, that is, for equivalent elements in the
5572   *  two ranges, elements from the first range will always come
5573   *  before elements from the second.
5574   *
5575   *  The comparison function should have the same effects on ordering as
5576   *  the function used for the initial sort.
5577  */
5578  template<typename _InputIterator1, typename _InputIterator2,
5579	   typename _OutputIterator, typename _Compare>
5580    _OutputIterator
5581    merge(_InputIterator1 __first1, _InputIterator1 __last1,
5582	  _InputIterator2 __first2, _InputIterator2 __last2,
5583	  _OutputIterator __result, _Compare __comp)
5584    {
5585      typedef typename iterator_traits<_InputIterator1>::value_type
5586	_ValueType1;
5587      typedef typename iterator_traits<_InputIterator2>::value_type
5588	_ValueType2;
5589
5590      // concept requirements
5591      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
5592      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
5593      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
5594				  _ValueType1>)
5595      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
5596				  _ValueType2>)
5597      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
5598				  _ValueType2, _ValueType1>)
5599      __glibcxx_requires_sorted_set_pred(__first1, __last1, __first2, __comp);
5600      __glibcxx_requires_sorted_set_pred(__first2, __last2, __first1, __comp);
5601
5602      while (__first1 != __last1 && __first2 != __last2)
5603	{
5604	  if (__comp(*__first2, *__first1))
5605	    {
5606	      *__result = *__first2;
5607	      ++__first2;
5608	    }
5609	  else
5610	    {
5611	      *__result = *__first1;
5612	      ++__first1;
5613	    }
5614	  ++__result;
5615	}
5616      return std::copy(__first2, __last2, std::copy(__first1, __last1,
5617						    __result));
5618    }
5619
5620
5621  /**
5622   *  @brief Sort the elements of a sequence, preserving the relative order
5623   *         of equivalent elements.
5624   *  @ingroup sorting_algorithms
5625   *  @param  __first   An iterator.
5626   *  @param  __last    Another iterator.
5627   *  @return  Nothing.
5628   *
5629   *  Sorts the elements in the range @p [__first,__last) in ascending order,
5630   *  such that for each iterator @p i in the range @p [__first,__last-1),
5631   *  @p *(i+1)<*i is false.
5632   *
5633   *  The relative ordering of equivalent elements is preserved, so any two
5634   *  elements @p x and @p y in the range @p [__first,__last) such that
5635   *  @p x<y is false and @p y<x is false will have the same relative
5636   *  ordering after calling @p stable_sort().
5637  */
5638  template<typename _RandomAccessIterator>
5639    inline void
5640    stable_sort(_RandomAccessIterator __first, _RandomAccessIterator __last)
5641    {
5642      typedef typename iterator_traits<_RandomAccessIterator>::value_type
5643	_ValueType;
5644      typedef typename iterator_traits<_RandomAccessIterator>::difference_type
5645	_DistanceType;
5646
5647      // concept requirements
5648      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
5649	    _RandomAccessIterator>)
5650      __glibcxx_function_requires(_LessThanComparableConcept<_ValueType>)
5651      __glibcxx_requires_valid_range(__first, __last);
5652
5653      _Temporary_buffer<_RandomAccessIterator, _ValueType> __buf(__first,
5654								 __last);
5655      if (__buf.begin() == 0)
5656	std::__inplace_stable_sort(__first, __last);
5657      else
5658	std::__stable_sort_adaptive(__first, __last, __buf.begin(),
5659				    _DistanceType(__buf.size()));
5660    }
5661
5662  /**
5663   *  @brief Sort the elements of a sequence using a predicate for comparison,
5664   *         preserving the relative order of equivalent elements.
5665   *  @ingroup sorting_algorithms
5666   *  @param  __first   An iterator.
5667   *  @param  __last    Another iterator.
5668   *  @param  __comp    A comparison functor.
5669   *  @return  Nothing.
5670   *
5671   *  Sorts the elements in the range @p [__first,__last) in ascending order,
5672   *  such that for each iterator @p i in the range @p [__first,__last-1),
5673   *  @p __comp(*(i+1),*i) is false.
5674   *
5675   *  The relative ordering of equivalent elements is preserved, so any two
5676   *  elements @p x and @p y in the range @p [__first,__last) such that
5677   *  @p __comp(x,y) is false and @p __comp(y,x) is false will have the same
5678   *  relative ordering after calling @p stable_sort().
5679  */
5680  template<typename _RandomAccessIterator, typename _Compare>
5681    inline void
5682    stable_sort(_RandomAccessIterator __first, _RandomAccessIterator __last,
5683		_Compare __comp)
5684    {
5685      typedef typename iterator_traits<_RandomAccessIterator>::value_type
5686	_ValueType;
5687      typedef typename iterator_traits<_RandomAccessIterator>::difference_type
5688	_DistanceType;
5689
5690      // concept requirements
5691      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
5692	    _RandomAccessIterator>)
5693      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
5694				  _ValueType,
5695				  _ValueType>)
5696      __glibcxx_requires_valid_range(__first, __last);
5697
5698      _Temporary_buffer<_RandomAccessIterator, _ValueType> __buf(__first,
5699								 __last);
5700      if (__buf.begin() == 0)
5701	std::__inplace_stable_sort(__first, __last, __comp);
5702      else
5703	std::__stable_sort_adaptive(__first, __last, __buf.begin(),
5704				    _DistanceType(__buf.size()), __comp);
5705    }
5706
5707
5708  /**
5709   *  @brief Return the union of two sorted ranges.
5710   *  @ingroup set_algorithms
5711   *  @param  __first1  Start of first range.
5712   *  @param  __last1   End of first range.
5713   *  @param  __first2  Start of second range.
5714   *  @param  __last2   End of second range.
5715   *  @return  End of the output range.
5716   *  @ingroup set_algorithms
5717   *
5718   *  This operation iterates over both ranges, copying elements present in
5719   *  each range in order to the output range.  Iterators increment for each
5720   *  range.  When the current element of one range is less than the other,
5721   *  that element is copied and the iterator advanced.  If an element is
5722   *  contained in both ranges, the element from the first range is copied and
5723   *  both ranges advance.  The output range may not overlap either input
5724   *  range.
5725  */
5726  template<typename _InputIterator1, typename _InputIterator2,
5727	   typename _OutputIterator>
5728    _OutputIterator
5729    set_union(_InputIterator1 __first1, _InputIterator1 __last1,
5730	      _InputIterator2 __first2, _InputIterator2 __last2,
5731	      _OutputIterator __result)
5732    {
5733      typedef typename iterator_traits<_InputIterator1>::value_type
5734	_ValueType1;
5735      typedef typename iterator_traits<_InputIterator2>::value_type
5736	_ValueType2;
5737
5738      // concept requirements
5739      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
5740      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
5741      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
5742				  _ValueType1>)
5743      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
5744				  _ValueType2>)
5745      __glibcxx_function_requires(_LessThanOpConcept<_ValueType1, _ValueType2>)
5746      __glibcxx_function_requires(_LessThanOpConcept<_ValueType2, _ValueType1>)
5747      __glibcxx_requires_sorted_set(__first1, __last1, __first2);
5748      __glibcxx_requires_sorted_set(__first2, __last2, __first1);
5749
5750      while (__first1 != __last1 && __first2 != __last2)
5751	{
5752	  if (*__first1 < *__first2)
5753	    {
5754	      *__result = *__first1;
5755	      ++__first1;
5756	    }
5757	  else if (*__first2 < *__first1)
5758	    {
5759	      *__result = *__first2;
5760	      ++__first2;
5761	    }
5762	  else
5763	    {
5764	      *__result = *__first1;
5765	      ++__first1;
5766	      ++__first2;
5767	    }
5768	  ++__result;
5769	}
5770      return std::copy(__first2, __last2, std::copy(__first1, __last1,
5771						    __result));
5772    }
5773
5774  /**
5775   *  @brief Return the union of two sorted ranges using a comparison functor.
5776   *  @ingroup set_algorithms
5777   *  @param  __first1  Start of first range.
5778   *  @param  __last1   End of first range.
5779   *  @param  __first2  Start of second range.
5780   *  @param  __last2   End of second range.
5781   *  @param  __comp    The comparison functor.
5782   *  @return  End of the output range.
5783   *  @ingroup set_algorithms
5784   *
5785   *  This operation iterates over both ranges, copying elements present in
5786   *  each range in order to the output range.  Iterators increment for each
5787   *  range.  When the current element of one range is less than the other
5788   *  according to @p __comp, that element is copied and the iterator advanced.
5789   *  If an equivalent element according to @p __comp is contained in both
5790   *  ranges, the element from the first range is copied and both ranges
5791   *  advance.  The output range may not overlap either input range.
5792  */
5793  template<typename _InputIterator1, typename _InputIterator2,
5794	   typename _OutputIterator, typename _Compare>
5795    _OutputIterator
5796    set_union(_InputIterator1 __first1, _InputIterator1 __last1,
5797	      _InputIterator2 __first2, _InputIterator2 __last2,
5798	      _OutputIterator __result, _Compare __comp)
5799    {
5800      typedef typename iterator_traits<_InputIterator1>::value_type
5801	_ValueType1;
5802      typedef typename iterator_traits<_InputIterator2>::value_type
5803	_ValueType2;
5804
5805      // concept requirements
5806      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
5807      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
5808      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
5809				  _ValueType1>)
5810      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
5811				  _ValueType2>)
5812      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
5813				  _ValueType1, _ValueType2>)
5814      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
5815				  _ValueType2, _ValueType1>)
5816      __glibcxx_requires_sorted_set_pred(__first1, __last1, __first2, __comp);
5817      __glibcxx_requires_sorted_set_pred(__first2, __last2, __first1, __comp);
5818
5819      while (__first1 != __last1 && __first2 != __last2)
5820	{
5821	  if (__comp(*__first1, *__first2))
5822	    {
5823	      *__result = *__first1;
5824	      ++__first1;
5825	    }
5826	  else if (__comp(*__first2, *__first1))
5827	    {
5828	      *__result = *__first2;
5829	      ++__first2;
5830	    }
5831	  else
5832	    {
5833	      *__result = *__first1;
5834	      ++__first1;
5835	      ++__first2;
5836	    }
5837	  ++__result;
5838	}
5839      return std::copy(__first2, __last2, std::copy(__first1, __last1,
5840						    __result));
5841    }
5842
5843  /**
5844   *  @brief Return the intersection of two sorted ranges.
5845   *  @ingroup set_algorithms
5846   *  @param  __first1  Start of first range.
5847   *  @param  __last1   End of first range.
5848   *  @param  __first2  Start of second range.
5849   *  @param  __last2   End of second range.
5850   *  @return  End of the output range.
5851   *  @ingroup set_algorithms
5852   *
5853   *  This operation iterates over both ranges, copying elements present in
5854   *  both ranges in order to the output range.  Iterators increment for each
5855   *  range.  When the current element of one range is less than the other,
5856   *  that iterator advances.  If an element is contained in both ranges, the
5857   *  element from the first range is copied and both ranges advance.  The
5858   *  output range may not overlap either input range.
5859  */
5860  template<typename _InputIterator1, typename _InputIterator2,
5861	   typename _OutputIterator>
5862    _OutputIterator
5863    set_intersection(_InputIterator1 __first1, _InputIterator1 __last1,
5864		     _InputIterator2 __first2, _InputIterator2 __last2,
5865		     _OutputIterator __result)
5866    {
5867      typedef typename iterator_traits<_InputIterator1>::value_type
5868	_ValueType1;
5869      typedef typename iterator_traits<_InputIterator2>::value_type
5870	_ValueType2;
5871
5872      // concept requirements
5873      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
5874      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
5875      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
5876				  _ValueType1>)
5877      __glibcxx_function_requires(_LessThanOpConcept<_ValueType1, _ValueType2>)
5878      __glibcxx_function_requires(_LessThanOpConcept<_ValueType2, _ValueType1>)
5879      __glibcxx_requires_sorted_set(__first1, __last1, __first2);
5880      __glibcxx_requires_sorted_set(__first2, __last2, __first1);
5881
5882      while (__first1 != __last1 && __first2 != __last2)
5883	if (*__first1 < *__first2)
5884	  ++__first1;
5885	else if (*__first2 < *__first1)
5886	  ++__first2;
5887	else
5888	  {
5889	    *__result = *__first1;
5890	    ++__first1;
5891	    ++__first2;
5892	    ++__result;
5893	  }
5894      return __result;
5895    }
5896
5897  /**
5898   *  @brief Return the intersection of two sorted ranges using comparison
5899   *  functor.
5900   *  @ingroup set_algorithms
5901   *  @param  __first1  Start of first range.
5902   *  @param  __last1   End of first range.
5903   *  @param  __first2  Start of second range.
5904   *  @param  __last2   End of second range.
5905   *  @param  __comp    The comparison functor.
5906   *  @return  End of the output range.
5907   *  @ingroup set_algorithms
5908   *
5909   *  This operation iterates over both ranges, copying elements present in
5910   *  both ranges in order to the output range.  Iterators increment for each
5911   *  range.  When the current element of one range is less than the other
5912   *  according to @p __comp, that iterator advances.  If an element is
5913   *  contained in both ranges according to @p __comp, the element from the
5914   *  first range is copied and both ranges advance.  The output range may not
5915   *  overlap either input range.
5916  */
5917  template<typename _InputIterator1, typename _InputIterator2,
5918	   typename _OutputIterator, typename _Compare>
5919    _OutputIterator
5920    set_intersection(_InputIterator1 __first1, _InputIterator1 __last1,
5921		     _InputIterator2 __first2, _InputIterator2 __last2,
5922		     _OutputIterator __result, _Compare __comp)
5923    {
5924      typedef typename iterator_traits<_InputIterator1>::value_type
5925	_ValueType1;
5926      typedef typename iterator_traits<_InputIterator2>::value_type
5927	_ValueType2;
5928
5929      // concept requirements
5930      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
5931      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
5932      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
5933				  _ValueType1>)
5934      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
5935				  _ValueType1, _ValueType2>)
5936      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
5937				  _ValueType2, _ValueType1>)
5938      __glibcxx_requires_sorted_set_pred(__first1, __last1, __first2, __comp);
5939      __glibcxx_requires_sorted_set_pred(__first2, __last2, __first1, __comp);
5940
5941      while (__first1 != __last1 && __first2 != __last2)
5942	if (__comp(*__first1, *__first2))
5943	  ++__first1;
5944	else if (__comp(*__first2, *__first1))
5945	  ++__first2;
5946	else
5947	  {
5948	    *__result = *__first1;
5949	    ++__first1;
5950	    ++__first2;
5951	    ++__result;
5952	  }
5953      return __result;
5954    }
5955
5956  /**
5957   *  @brief Return the difference of two sorted ranges.
5958   *  @ingroup set_algorithms
5959   *  @param  __first1  Start of first range.
5960   *  @param  __last1   End of first range.
5961   *  @param  __first2  Start of second range.
5962   *  @param  __last2   End of second range.
5963   *  @return  End of the output range.
5964   *  @ingroup set_algorithms
5965   *
5966   *  This operation iterates over both ranges, copying elements present in
5967   *  the first range but not the second in order to the output range.
5968   *  Iterators increment for each range.  When the current element of the
5969   *  first range is less than the second, that element is copied and the
5970   *  iterator advances.  If the current element of the second range is less,
5971   *  the iterator advances, but no element is copied.  If an element is
5972   *  contained in both ranges, no elements are copied and both ranges
5973   *  advance.  The output range may not overlap either input range.
5974  */
5975  template<typename _InputIterator1, typename _InputIterator2,
5976	   typename _OutputIterator>
5977    _OutputIterator
5978    set_difference(_InputIterator1 __first1, _InputIterator1 __last1,
5979		   _InputIterator2 __first2, _InputIterator2 __last2,
5980		   _OutputIterator __result)
5981    {
5982      typedef typename iterator_traits<_InputIterator1>::value_type
5983	_ValueType1;
5984      typedef typename iterator_traits<_InputIterator2>::value_type
5985	_ValueType2;
5986
5987      // concept requirements
5988      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
5989      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
5990      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
5991				  _ValueType1>)
5992      __glibcxx_function_requires(_LessThanOpConcept<_ValueType1, _ValueType2>)
5993      __glibcxx_function_requires(_LessThanOpConcept<_ValueType2, _ValueType1>)
5994      __glibcxx_requires_sorted_set(__first1, __last1, __first2);
5995      __glibcxx_requires_sorted_set(__first2, __last2, __first1);
5996
5997      while (__first1 != __last1 && __first2 != __last2)
5998	if (*__first1 < *__first2)
5999	  {
6000	    *__result = *__first1;
6001	    ++__first1;
6002	    ++__result;
6003	  }
6004	else if (*__first2 < *__first1)
6005	  ++__first2;
6006	else
6007	  {
6008	    ++__first1;
6009	    ++__first2;
6010	  }
6011      return std::copy(__first1, __last1, __result);
6012    }
6013
6014  /**
6015   *  @brief  Return the difference of two sorted ranges using comparison
6016   *  functor.
6017   *  @ingroup set_algorithms
6018   *  @param  __first1  Start of first range.
6019   *  @param  __last1   End of first range.
6020   *  @param  __first2  Start of second range.
6021   *  @param  __last2   End of second range.
6022   *  @param  __comp    The comparison functor.
6023   *  @return  End of the output range.
6024   *  @ingroup set_algorithms
6025   *
6026   *  This operation iterates over both ranges, copying elements present in
6027   *  the first range but not the second in order to the output range.
6028   *  Iterators increment for each range.  When the current element of the
6029   *  first range is less than the second according to @p __comp, that element
6030   *  is copied and the iterator advances.  If the current element of the
6031   *  second range is less, no element is copied and the iterator advances.
6032   *  If an element is contained in both ranges according to @p __comp, no
6033   *  elements are copied and both ranges advance.  The output range may not
6034   *  overlap either input range.
6035  */
6036  template<typename _InputIterator1, typename _InputIterator2,
6037	   typename _OutputIterator, typename _Compare>
6038    _OutputIterator
6039    set_difference(_InputIterator1 __first1, _InputIterator1 __last1,
6040		   _InputIterator2 __first2, _InputIterator2 __last2,
6041		   _OutputIterator __result, _Compare __comp)
6042    {
6043      typedef typename iterator_traits<_InputIterator1>::value_type
6044	_ValueType1;
6045      typedef typename iterator_traits<_InputIterator2>::value_type
6046	_ValueType2;
6047
6048      // concept requirements
6049      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
6050      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
6051      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
6052				  _ValueType1>)
6053      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
6054				  _ValueType1, _ValueType2>)
6055      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
6056				  _ValueType2, _ValueType1>)
6057      __glibcxx_requires_sorted_set_pred(__first1, __last1, __first2, __comp);
6058      __glibcxx_requires_sorted_set_pred(__first2, __last2, __first1, __comp);
6059
6060      while (__first1 != __last1 && __first2 != __last2)
6061	if (__comp(*__first1, *__first2))
6062	  {
6063	    *__result = *__first1;
6064	    ++__first1;
6065	    ++__result;
6066	  }
6067	else if (__comp(*__first2, *__first1))
6068	  ++__first2;
6069	else
6070	  {
6071	    ++__first1;
6072	    ++__first2;
6073	  }
6074      return std::copy(__first1, __last1, __result);
6075    }
6076
6077  /**
6078   *  @brief  Return the symmetric difference of two sorted ranges.
6079   *  @ingroup set_algorithms
6080   *  @param  __first1  Start of first range.
6081   *  @param  __last1   End of first range.
6082   *  @param  __first2  Start of second range.
6083   *  @param  __last2   End of second range.
6084   *  @return  End of the output range.
6085   *  @ingroup set_algorithms
6086   *
6087   *  This operation iterates over both ranges, copying elements present in
6088   *  one range but not the other in order to the output range.  Iterators
6089   *  increment for each range.  When the current element of one range is less
6090   *  than the other, that element is copied and the iterator advances.  If an
6091   *  element is contained in both ranges, no elements are copied and both
6092   *  ranges advance.  The output range may not overlap either input range.
6093  */
6094  template<typename _InputIterator1, typename _InputIterator2,
6095	   typename _OutputIterator>
6096    _OutputIterator
6097    set_symmetric_difference(_InputIterator1 __first1, _InputIterator1 __last1,
6098			     _InputIterator2 __first2, _InputIterator2 __last2,
6099			     _OutputIterator __result)
6100    {
6101      typedef typename iterator_traits<_InputIterator1>::value_type
6102	_ValueType1;
6103      typedef typename iterator_traits<_InputIterator2>::value_type
6104	_ValueType2;
6105
6106      // concept requirements
6107      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
6108      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
6109      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
6110				  _ValueType1>)
6111      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
6112				  _ValueType2>)
6113      __glibcxx_function_requires(_LessThanOpConcept<_ValueType1, _ValueType2>)
6114      __glibcxx_function_requires(_LessThanOpConcept<_ValueType2, _ValueType1>)
6115      __glibcxx_requires_sorted_set(__first1, __last1, __first2);
6116      __glibcxx_requires_sorted_set(__first2, __last2, __first1);
6117
6118      while (__first1 != __last1 && __first2 != __last2)
6119	if (*__first1 < *__first2)
6120	  {
6121	    *__result = *__first1;
6122	    ++__first1;
6123	    ++__result;
6124	  }
6125	else if (*__first2 < *__first1)
6126	  {
6127	    *__result = *__first2;
6128	    ++__first2;
6129	    ++__result;
6130	  }
6131	else
6132	  {
6133	    ++__first1;
6134	    ++__first2;
6135	  }
6136      return std::copy(__first2, __last2, std::copy(__first1,
6137						    __last1, __result));
6138    }
6139
6140  /**
6141   *  @brief  Return the symmetric difference of two sorted ranges using
6142   *  comparison functor.
6143   *  @ingroup set_algorithms
6144   *  @param  __first1  Start of first range.
6145   *  @param  __last1   End of first range.
6146   *  @param  __first2  Start of second range.
6147   *  @param  __last2   End of second range.
6148   *  @param  __comp    The comparison functor.
6149   *  @return  End of the output range.
6150   *  @ingroup set_algorithms
6151   *
6152   *  This operation iterates over both ranges, copying elements present in
6153   *  one range but not the other in order to the output range.  Iterators
6154   *  increment for each range.  When the current element of one range is less
6155   *  than the other according to @p comp, that element is copied and the
6156   *  iterator advances.  If an element is contained in both ranges according
6157   *  to @p __comp, no elements are copied and both ranges advance.  The output
6158   *  range may not overlap either input range.
6159  */
6160  template<typename _InputIterator1, typename _InputIterator2,
6161	   typename _OutputIterator, typename _Compare>
6162    _OutputIterator
6163    set_symmetric_difference(_InputIterator1 __first1, _InputIterator1 __last1,
6164			     _InputIterator2 __first2, _InputIterator2 __last2,
6165			     _OutputIterator __result,
6166			     _Compare __comp)
6167    {
6168      typedef typename iterator_traits<_InputIterator1>::value_type
6169	_ValueType1;
6170      typedef typename iterator_traits<_InputIterator2>::value_type
6171	_ValueType2;
6172
6173      // concept requirements
6174      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
6175      __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
6176      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
6177				  _ValueType1>)
6178      __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
6179				  _ValueType2>)
6180      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
6181				  _ValueType1, _ValueType2>)
6182      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
6183				  _ValueType2, _ValueType1>)
6184      __glibcxx_requires_sorted_set_pred(__first1, __last1, __first2, __comp);
6185      __glibcxx_requires_sorted_set_pred(__first2, __last2, __first1, __comp);
6186
6187      while (__first1 != __last1 && __first2 != __last2)
6188	if (__comp(*__first1, *__first2))
6189	  {
6190	    *__result = *__first1;
6191	    ++__first1;
6192	    ++__result;
6193	  }
6194	else if (__comp(*__first2, *__first1))
6195	  {
6196	    *__result = *__first2;
6197	    ++__first2;
6198	    ++__result;
6199	  }
6200	else
6201	  {
6202	    ++__first1;
6203	    ++__first2;
6204	  }
6205      return std::copy(__first2, __last2,
6206		       std::copy(__first1, __last1, __result));
6207    }
6208
6209
6210  /**
6211   *  @brief  Return the minimum element in a range.
6212   *  @ingroup sorting_algorithms
6213   *  @param  __first  Start of range.
6214   *  @param  __last   End of range.
6215   *  @return  Iterator referencing the first instance of the smallest value.
6216  */
6217  template<typename _ForwardIterator>
6218    _ForwardIterator
6219    min_element(_ForwardIterator __first, _ForwardIterator __last)
6220    {
6221      // concept requirements
6222      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
6223      __glibcxx_function_requires(_LessThanComparableConcept<
6224	    typename iterator_traits<_ForwardIterator>::value_type>)
6225      __glibcxx_requires_valid_range(__first, __last);
6226
6227      if (__first == __last)
6228	return __first;
6229      _ForwardIterator __result = __first;
6230      while (++__first != __last)
6231	if (*__first < *__result)
6232	  __result = __first;
6233      return __result;
6234    }
6235
6236  /**
6237   *  @brief  Return the minimum element in a range using comparison functor.
6238   *  @ingroup sorting_algorithms
6239   *  @param  __first  Start of range.
6240   *  @param  __last   End of range.
6241   *  @param  __comp   Comparison functor.
6242   *  @return  Iterator referencing the first instance of the smallest value
6243   *  according to __comp.
6244  */
6245  template<typename _ForwardIterator, typename _Compare>
6246    _ForwardIterator
6247    min_element(_ForwardIterator __first, _ForwardIterator __last,
6248		_Compare __comp)
6249    {
6250      // concept requirements
6251      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
6252      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
6253	    typename iterator_traits<_ForwardIterator>::value_type,
6254	    typename iterator_traits<_ForwardIterator>::value_type>)
6255      __glibcxx_requires_valid_range(__first, __last);
6256
6257      if (__first == __last)
6258	return __first;
6259      _ForwardIterator __result = __first;
6260      while (++__first != __last)
6261	if (__comp(*__first, *__result))
6262	  __result = __first;
6263      return __result;
6264    }
6265
6266  /**
6267   *  @brief  Return the maximum element in a range.
6268   *  @ingroup sorting_algorithms
6269   *  @param  __first  Start of range.
6270   *  @param  __last   End of range.
6271   *  @return  Iterator referencing the first instance of the largest value.
6272  */
6273  template<typename _ForwardIterator>
6274    _ForwardIterator
6275    max_element(_ForwardIterator __first, _ForwardIterator __last)
6276    {
6277      // concept requirements
6278      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
6279      __glibcxx_function_requires(_LessThanComparableConcept<
6280	    typename iterator_traits<_ForwardIterator>::value_type>)
6281      __glibcxx_requires_valid_range(__first, __last);
6282
6283      if (__first == __last)
6284	return __first;
6285      _ForwardIterator __result = __first;
6286      while (++__first != __last)
6287	if (*__result < *__first)
6288	  __result = __first;
6289      return __result;
6290    }
6291
6292  /**
6293   *  @brief  Return the maximum element in a range using comparison functor.
6294   *  @ingroup sorting_algorithms
6295   *  @param  __first  Start of range.
6296   *  @param  __last   End of range.
6297   *  @param  __comp   Comparison functor.
6298   *  @return  Iterator referencing the first instance of the largest value
6299   *  according to __comp.
6300  */
6301  template<typename _ForwardIterator, typename _Compare>
6302    _ForwardIterator
6303    max_element(_ForwardIterator __first, _ForwardIterator __last,
6304		_Compare __comp)
6305    {
6306      // concept requirements
6307      __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
6308      __glibcxx_function_requires(_BinaryPredicateConcept<_Compare,
6309	    typename iterator_traits<_ForwardIterator>::value_type,
6310	    typename iterator_traits<_ForwardIterator>::value_type>)
6311      __glibcxx_requires_valid_range(__first, __last);
6312
6313      if (__first == __last) return __first;
6314      _ForwardIterator __result = __first;
6315      while (++__first != __last)
6316	if (__comp(*__result, *__first))
6317	  __result = __first;
6318      return __result;
6319    }
6320
6321_GLIBCXX_END_NAMESPACE_ALGO
6322} // namespace std
6323
6324#endif /* _STL_ALGO_H */
6325